There is some time limit on changing the thread title (but I don't know what it is or how it works). You normally can change the title on a newly created thread within a few minutes. I think once somebody replied to it, or when the limit expires (such as a "cron" job copying files once an hour), the thread title is frozen and can only be changed by admins (or so I think).
'63 2600 Touring Spider (AR 191437, the car that started the 2000/2600 International Register, reassembly in progress)
ex-'65 2600 SZ (AR 856043, now being restored in Austria)
Maintainer of a private 2600 SZ register (not the one in the Netherlands).