1) Each obligation relationship just as every legal relationship lasts in time. Universality of this feature means that it does not constitute a sufficient criterion for distinguishing any kinds (types) of obligations.

2) Distinguishing categories for permanent legal relationships is useful for inter-temporal law and for describing particular legal cases, in which duration in time determines duties and rights of the parties involved and the legal effects occurring with time are not subject to revocation.

3) Continuous obligation shall not be replaced by the term “permanent obligation”. The name implies a permanent character of this form of obligation relationship, whereas in a general meaning the construct of continuous obligation displays neither permanency nor temporality characteristics.

4) The term “continuous obligation” is a legal term (art. 3651 and 3841 of the Civil Code) with non-statutory criteria of applicability, to all intents and purposes adopted by the doctrine. When defining the term one should take into account a far-reaching compatibility in thereof scope.

5) The definition should take into account the fact that continuous obligation constitutes one of the most general legal constructs as regards contractual law, which applies in the following cases: (1)  obligations corresponding to certain types of defined agreements, (2)  obligations corresponding to certain types of defined agreements, modified by the parties as regards the statutory character of performance, (3) obligations resulting from non-defined agreements with performance applicable for continuous obligation, (4)  ex lege obligations with performance applicable for continuous obligation.

6) The criterion of performance should be the basis for distinguishing the category of continuous obligation. Such approach takes into consideration the existing definition of the term “continuous obligation” and also complies with the art. 353 of the Civil Code, according to which performance is one of the essential elements intended for obligation relationship.

7) Continuous obligation is a type of obligation in which the time factor influences the scope of performance (performances). Therefore, it is an obligation whose inherent element is one of the following performances: a continuous performance, a temporary performance or successive performances. The time factor is a constitutive element of a continuous obligation. It may apply both in the particular performance (continuous performance and temporary performance), and in the general scope of due performances pursuing the obligation relationship (temporary performances and successive performances).

8) An obligation relationship may be qualified as a continuous one on the basis of main performance or collateral performance.

9) There are at least four distinguishable types (general models) in the category of continuous obligations: (1) model distinguished regarding the source of obligation relationship; this model can include obligations resulting from a legal act or statutory obligations, which are usually specified by further legal occurrences such as court ruling, consequential legal act or administrative decision; (2) model distinguished regarding the type of performance (performances) which constitutes an element of the obligation; (3) model distinguished regarding self-executing/non-self-executing type of the continuous obligation; (4) model distinguished regarding the manner of determining the duration of the obligation relationship; this model involves continuous obligations whose duration is determined directly, which include obligations for specified and non-specified time, as well as continuous obligations, whose duration is indirectly determined. The scopes of the types of obligations mentioned above overlap.

10) Non-self-executing continuous obligation is specifically connected with another relationship (of legal-civil nature). A self-executing obligation does not reveal this feature.

11) Self-executing continuous obligations which result from statutory regulations include at least three types of obligations: (1) obligations according to which one party is liable to perform (2) obligations in which both parties are liable to perform, (3) obligations which after being entered into (directly or with delay) reveal all (or almost all) features of a contractual relationship.

12) Self-executing contractual continuous obligations constitute a major group of all continuous obligations. However, it does not justify identifying the whole category of obligations with this particular group of obligations.

13) The connection between non-self-executing continuous obligations and another legal relationship is apparently manifested in the time aspect – duration of the obligation is connected with duration of another legal relationship. However, this connection may reach further.

14) A group of non-self-executing continuous obligations is not homogenous. The relationship which is connected with a continuous obligation is both another obligation relationship and another relationship of legal-civil nature which is not an obligation relationship (e.g. a relationship of corporate type, right in rem relationship and right in family relationship). The connection with another legal relationship can manifest various levels of intensity. Non-self-executing obligation relationship may be derivative or auxiliary (sub-servient) towards another legal relationship or even necessary to maintain this relationship.

15) The category of non-self-executing continuous obligations does not include obligations which are established due to the expiration of an earlier legal relationship. However, when describing these relationships it is necessary to take into account a surrogate character of the obligation relationship.

16) Incorporating the element of time in the construct of a continuous obligation justifies the assumption that the content of this relationship (art. 56 of the Civil Code) is changeable in time. This particularly refers to continuous obligations of a long-term character. The element of time does not merely function to measure the duration and scope of the performance (performances). Time lapse may be a justification for adjusting the contents of the obligation relationship to the changes in socio-economic relationships, including the changes which are not connected with any extraordinary phenomena (art. 3571 of the Civil Code).