There are a couple of options for long tree straps. Some of them are more/less of an option depending on how you attach your suspension to the strap.
1) Use a strap with multiple attachment points like the "Slap Strap"
2) Wrap the strap around the tree multiple times.
3) Turn the strap so that the loop crossover isn't towards the hammock, but on the other side of the tree to use up additional slack
4) Tie a knot in the strap to use as a beaner hook. (many old school strappers are using this by default, as there are no loops at all on some straps)
5) Use D/climbing rings for a similar purpose (make sure they can hold your weight!)