You'll need more time on HL maps later on, when it's the late game and you have to act with many heroes and perform many operations.
In the late game, you'll have 2 hours + 10 minutes per turn, and battles will likely be no more than 10 seconds. Of course, you can have a quality game, and I don't even argue that this time can be spent wisely, but it's still unlimited.
P.S. I'll remind you that in the actual rules, it's 8 minutes, although many play with 10, but still...