What happens when I download app number 149 for iPhone?

It wont let you.

you’ll be able to install it just fine, it just wont be accessible/visible until you delete another app so it can take the deleted app’s place.

(And if you happen to be interested in jailbreaking, that gives you [among many other useful apps] a free app called BossPrefs that lets you hide apps so they don’t display in the Springboard. You can unhide an app at any time. That’s cool because there are probably a few of the undeletable Apple apps that you don’t use, or apps you would like to keep installed but only use once in a blue moon.)

I keep all my extra Apps stored in my iTunes. I have around 1,500 + free apps. Sitting there. Some I only use when I travel. Others are for stuff which may come in handy at a later date.

There are many times when apps are temporarily price-reduced by their developers for a short amt. of time. So if I think I may have use for it, I grab it if it’s price cut down to free. Why not?

There is a free app called Pandorabox which had daily listings of price cut apps and I check it regularly. Give it a try.