Want to run #10 gauge wire 25 feet to a large window unit that heats and cools. Is the distance too far for #10 wire.

Yes.

Well the question is not clear.

A) Does the unit require a 30A circuit?
B) Or does the unit draw 30A?

If A), then 25 feet is not at all too far.
If B), then #10 is not large enough, you need #8.

The bottom line is what does the rating plate on the unit state as far as minimum circuit ampacity and maximum fuse or breaker?