The profound understanding of the mechanisms that affect the thermomechanical response of liquid-crystalline elastomers is of significant importance for applications. In the vicinity of a phase transition this response is reflected to the thermodynamic critical behavior. We demonstrate that two main-chain liquid-crystalline elastomers of identical composition, crosslinked in temperatures corresponding to different thermodynamic phases, exhibit dramatically different thermal behavior as derived from high-resolution calorimetry. Hence, a previously unexplored parameter for controlling the elastomers critical behavior is revealed, exhibiting a very strong effect. Moreover, the relative strength of various discovered mechanisms that control the critical behavior is discussed.