Stereo Subwoofer Pairing


Does it matter if stereo subwoofers (one dedicated for each channel) are the same age or will it sound fine to use one subwoofer that is new with a used one (both subwoofers are the same model)?

Will it just take time for the new subwoofer to break in to match the used one or will they never sound close to each other?
rjb1101
I'm thinking about using either a used Rel T7 and a new Rel T7i or a used Rel T5i and a new Rel T5i with Magnepan .7's.  I have the T7 and the T5i in different systems right now.
Followup question on Rel's specifically.  Can I use a new i edition of the T series with the old T series?  Or are the model changes major enough that they won't sound similar.