Question

with heatran using struggle after no more pp in any other move, if given the chance would it go forever?

Answer 1

Struggle has a recoil that takes 1/4 of its HP, so it will die in 4 turns.

But... If you could heal it somehow, then yes it would, since Struggle has infinite PP.

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\m/o_o\m/

Answer 2

No.
Struggle takes away 1/4 of your HP every turn you use it. So in 4-5 turns, you would faint. If you had some way to heal, Struggle can be prolonged.