Does it make any difference if you have been flying twins but not pistons in the mean time?
Apparently not; it is the validity of the class or type rating that matters, not any other experience you may have gained in the meantime.
The hard law is in FCL.740:
(b) Renewal. If a class or type rating has expired, the applicant shall:
(1) take refresher training at an ATO, when necessary to reach the level of proficiency necessary to safely operate the relevant class or type of aircraft.
Currently the only acceptable means of complying with this law is in AMC1 FCL.740(b)(1):
(3)...
(i)...
(ii)...
(iii)...
(iv) expiry longer than 3 years: the applicant should again undergo the training required for the initial issue of the rating....
Of course, it is always possible for anyone to propose an alternative means of compliance to the competent authority but, until that is done and accepted, this will remain the only acceptable means.