Well I guess it depends on how long those "once or twice" times were. The reforms are based on the number of turns elapsed and not the actual year as represented in game so if you played for a significant length of time without the script then the reform script might only think you are in the year 200BC for example. Thats why you really need to put it on every time.

It should be second nature to check your cities and things before you end turn and the little pop-up advisor should remind you to turn the script on. I have trouble imagining how you could play for too long without getting annoyed at the damn pop-up =)

Also, just check your cities and scroll down the building list to see if the 'Marian Reform' marker has been placed. Sometimes it may not be quite so obvious that they have occured.....maybe.