mixing 80 and 100 and autogas...?

Reviewing some of the old posts on rec.aviation.owning, it appears
that the conventional wisdom is that mixing of the gases is ok.
What I foresee is that I can get 80 at my home field, but will need to
top off or completely fill up with 100LL as I go along. Is this truly
ok?

Are people still adding TCP to their tanks when using 100LL even if
they have a partial load of 80 on board?

I'm trying to avoid ever having a stuck exhaust valve again, but the
reality is that 80 is hard to find and autogas is frequently not an
option (depending on the airport).

Thanks,
Ryan