The true validity of a tre sim is still quite a mistery.
In theory, a sim activated before may 2006 has a validity of 12 months after last recharge, instead of a sim activated after may 2006 has 5 months (+1 only for incoming calls/sms) after last billed event.
But, there's always a but, is not unusual that a sim can lives 2 o 3 year without any recharge or event, or being deactivated before the end of validity, just only if not used for a bit.
I can only suggest you to write a mail (servizioclienti@tre.it), but probably will be difficult to get something
