I have found that pushing the temp early on gives the most character when the yeast is in a growth phase,
weather pushing it at any stage gives you the spice or the banana or even pear notes in the belgians, is something that has to be experiemented with on a yeas by yeast basis. the duvel strain can take a flogging temp wise, like a saison, but a similar strain will be horrible
anyway
I am pretty conservative with my Belgian fermentation profile, i pitch at 18 and let the beer free rise to 20, and hold it there. I would never let it go over 22 unless i knew the outcome beforehand.