I do individual logs for most of my geocaches. Every now and then we do power trails where we snag 90-200 geocaches in a day. I don't do individual logs as there really isn't anything interesting to say. If there is something noteworthy, I go back and edit my log accordingly.
The reason I am asking the questions is a group of us are doing the ET Highway in May. We will get 2,400 geocaches in five days. How many caches will we get each day? I have no way of knowing. However, if I can press "Found It" on my Garmin Montana then when I get home I will have a file that reflects what caches I got each day. I can then process a mass logging using the correct date. The cache owners of this power trail actually prefer a nice log on the first or last cache and then copy/paste logs for all others.
My other alternative is to purchase a cheap laptop and use GSAK.