I went to th10 when I had low 20s heroes but that's when I had all the other buildings maxed (always had a builder upping a hero). A couple tips I could give are...
1) Heroes are a freebie troop so higher the better!
2) If your clan wars, there is less pressure attacking as a th9 vs th9 than th10 vs th10 so staying lower is easier
3) As a th9, you can attack th7s with full collectors/storages and dead th8-10 bases for loot. Th10 is one less base option. Lots of loot for walls and research after maxing buildings.
4) If you normally jump between games after a few months, just get heroes to somewhere between 15-20 and then you can use them every hour instead of once a week.
5) If you think you're going to be playing for a year, dedicate a builder for them. Other people in your clan who are skipping heroes will be passing you up in war ranking (again less pressure), but later on they will have idle builders, low heroes, go th10, and suck horribly.
