According to the specs, the 5.5-22x has 100 minutes, and the 3.5-15x has 110 minutes elevation total.
You're right, any windage dialed will bring the erector over to one side and reduce the overall elevation available.
I rarely use over 15x, so if I were going to buy another NF, it would be the 3.5-15x50mm. In fact, that's what Iordered for my AI before buying the SN3.
If you have the cash and want a noticable step up in optical quality (and features IMO) look at the SN3's or the new two-turn S&B. They are about 2x the cost of the NF, but we're already talking about expensive rifles to both build up and feed. These "one/two turn" scopes zero in a different manner than the NF/Leupold elevation knobs which just run free the entire range. You generally set the base point for the first turn (ie, a zero stop) and then the total "up" elevation is limited by the number of turns in the knob instead of the erector hitting the tube, as long as you have the right base installed. It's nice because dialing back down to your primary zero is less error prone, and you also have more clicks per revolution. Also note that the NF has a second focal plane reticle, so ranging/holdoff can only be done at one power.
Just my impressions after trying a bunch of them...
-z