Are mods in vBulletin generally compadible between versions of vBulletin?

[n0b]

vBulletin 3.5
vBulletin 3.6
vBulletin 3.7

For the most part, are mods for 3.5 compatible between 3.5, 3.6 and 3.7? Or are the updates between the versions so extreme, that your website/forums will rely on an update to the mod in order to move on to the next version of vBulletin?

[CHIPIT]

I am running 3.5 and 3.6 mods on my 3.7 forum. I find they are generally reverse compatible, but there will be a few which will need updates to work.