Originally, I wasn't going to bring this up since it's getting considerably beyond what your average student undergoing OW certification might experience. However, it's well within the range of possibility for an experienced diver doing multiple dives which is where this discussion seems to be going.
One source of information that people may want to consider is the NOAA
Ascent To Altitude Table, which starts at 1000', and personally, I'd consider 800' to be close enough to start paying some attention. For a single 10m/30' dive (or even multiple successive dives), you can ascend immediately with a total nitrogen time of <100 min. That's probably difficult (although not impossible) for most people to achieve recreationally, but if you do exceed it, the required SI starts at 1:32.
However, if diving to 60'/20m, you hit the same time limit at 55 min total nitrogen time. That's starting to push it for one dive, but not all that unlikely for two dives with a one hour Surface Interval. As others have already pointed out in this thread, a 1:32 interval before you can ascend to altitude is not hard to meet by the time you get out of the water and cleaned up and what not, but if you hurried things, you might breach that limit if you weren't paying attention.
And if you're taking a helicopter ride to 1500', the total nitrogen time limit drops another letter group, and you might be looking at a 3 or 4 hour interval before ascending. At that point, the flight crew might be trading off risks of flying lower, or taking you higher sooner when you already have a medical condition severe enough to need the helicopter ride.