In reply to flopsicle:
Thanks for the clarification.
I think indoor routes are different again for several reasons:
1. We tend to have shorter sessions there (unlike going to the crag for a day)
2. Switching between belaying and climbing can happen really fast and you get very little rest.
3. There's the thought that this is a training session to get fitter/stronger rather than trying to tick a route.
4. The routes don't have names or permanence like on rock.
5. We tend to go back to our local walls far more regularly than a specific crag.
Because of this I've sometimes wondered what the best approach indoors is. I think for training value you definitely want to be climbing above your onsight grade a fair bit of the time. But at the same time I now think getting too pumped is counterproductive. If you get too pumped then you need to rest for too long and in a short session this means you do less climbing (or end up trying routes that are just too easy).
A lot of climbers seem to just stick to easier routes and do a fair bit of volume. Whilst good for endurance I don't think its that useful for getting stronger or upping one's grade. You end able to do more climbing but not necessarily harder climbing, and harder routes feature harder climbing, not more climbing.
My current approach is to try harder routes but with rests. If you do a route with one or two hangs you can think of it like doing several boulder problems in short succession. I try not to climb until I'm completely pumped and take a strategic rest before that happens. You can vary the time hanging to make each section just manageable. Gradually over successive sessions you can whittle the rests down to none, though usually at the start of the session, if its a route near your limit. The other tactic I use is to switch between different styles of routes each go. One time I might be doing a juggy roof, the next a crimpy wall. Because you're using different muscles in different ways (to some degree at least) its a bit like having more rest.