When you unpolymorph, you temporarily keep any intrinsics you had from that form and which you no longer have. How long it is before these intrinsics time out isn’t specified, but probably contains some random component so you can’t plan around when the intrinsic will lapse.

This was suggested for a hypothetical druid role, but noted that it doesn’t have to be a role-specific mechanic and could apply to other roles as well.