How does one evaluate when it is time to go for a level streaming technique?
Of course it depends on what is your target pc/console spec BUT still the question remains in a generic way:
Should my LOADED assets memory size be a percentage of GPU RAM? Close to 100%? That way, if I have a 2Gb GPU should I load my game in 2Gb chunks (or a little bit less for safety)? Or most of the time GPU processing limits will factor into play much earlier?
How does CPU memory/processor comes into this? How much the level itself is loaded into the CPU? Does the engine by itself has a large memory footprint?
Are disk acess speeds (hdd/sd read rate) an issue? Fast moving games (eg. racing) might have to load up the next part of the map faster than slower moving ones.
I fully expect that the answer to all of this is: IT DEPENDS! Neverthless are there any guidelines to this? For a small developer it is very hard (impossible?) to test your product in a large range of machine specs (consoles are simples on this regard).