If you render the top effect, it looks through and renders all the others with it, which is probably why it's taking a long time. You shouldn't be stepping in, rendering, stepping out, and rerendering. Just render the top effect.
Good advice Butcher. I make it a habit to mark in/out (before & after the section I want)then EXPERT RENDER everything (I have it mapped to F4 on the keyboard). The Avid will figure out what is really necessary for playback. Saves even more time since it will skip simple things like dissolves.
As Butcher said, if you have a lot of effects stacked, nested or collapsed (Avid FX too) it can take a while to render, because its doing all of them at once.
by top affect do you mean whats on on video 2 or 3 or the highest video track? or do you mean rendering the neseted affects on the inside the v1.2 doing those first or second?
Sort of both.....For example, if you have a nested effect in V1.1, V1.2 & v1.3 lets say, and a graphic in V2. I would normally select V3 (assuming you made one), mark an IN at the beginning and an OUT at the end, then choose EXPERT RENDER (it will automatically render a range). The Avid does a 'top down' look, realizes you're trying to render V3 (even if nothing is in V3) looks next at V2, then your nested EFX in V1.....it will render everything necessary in order for the clip to run correctly, you dont have to do anything else.
For reference in my 12 years cutting on an Avid Ive probably nested less than 50 times, but have never 'stepped into' a nested effect to render it [not that you couldnt]. Your making your life way to hard, the Avid is smart enough to 'combine' the effects if you were to just render the top layer.