I've found 5, 6 and 7 leaf clovers. Maybe even 8 and 9 leaf clovers. I'd have to look. When I find one four leaf, I usually find a few more in the same spot. I have found like 8 to 10 all at the same time/within minutes of each other. The last few times I found several at once, I put them in wax paper and ironed them. They have turned yellow in the wax paper, over time.
The ones put into books always seem to get busted up and broken, however, they hold the green color better.