Just be careful, have found custom fast transitions from theme customizer can remove some things from your transitions.ini file, editing the transitions.ini with lots of different things can cause the file to become unreadable.

If you feel confident use the hildon-desktop wiki to edit the values manually.

I normally manually change all the big values to 200 or 150.

Also before modifying anything backup.
Even better after a full reflash backup with backupmenu, when you've added your stuff backup again.
You have something to return to if something dies.