Depends a lot on what you spend it on. I'd say being a runescape millionaire's no longer anything special, if it ever was, but on the other hand 40m can buy a lot of stuff, especially 99's in firemaking, smithing, magic et al..
The weather conspired agaisnt me yesterday so I didn't get much computer time in (too hot and sticky) but still on course for 99 thieving in a couple of weeks - just in time for my holiday, in fact! Should be on later to get a couple of hours or more in.