The article "When it is not possible to choose a replacement employment contract" resolves some of the most common practical issues related to replacement employment contracts. 

It indicates that such a contract can only be safely concluded if an absent employee is replaced by a newly hired person. If, however, you need to replace someone who is temporarily transferred to another position, or the current employee is to be the deputy, it is better to stick to a contract for an indefinite period or conclude an "ordinary" contract for a fixed period. With the latter, you need to remember about the limit of 3 contracts and 33 months.

Moreover, the article includes recommendations on how to specify the duration of replacement contracts as safely as possible, also when we want to allow time for the transfer of responsibilities.
 

More in the article  r.pr. Katarzyna Dobkowska and adw. Natalii Basisty "When it is not possible to choose a replacement employment contract" for Rzeczpospolita (article from 24 March 2021).