@burnout426 Reducing the NUMBER of files in store to a third had little effect on the new size of a rebuilt lexicon. Deleting the few large files in store caused the lexicon to change size dramatically, from several times larger than store, to half the size of store. I think it must have been making a bad attempt at finding words in yenc encoding, which would essentially be a 3 million character word, or thousands of very long ones. I used to have binary groups in Opera and it usually coped. I think yenc just confuses it.
I don't really care if there's an 8GB store, but the problem is with a huge amount of random disk access when it's messing about trying to do whatever it's doing. Which puts disk usage to 100% continuously, and slows everything else down. This machine has a rotary drive, but my last one I had Opera on had an SSD, and suffered a similar problem. I don't really like the possibility of wearing out either type of drive, which I'm sure would happen if Opera continued at 100% usage 24/7.