Xavier In the 1970's through the 1980's most cell culture flasks and
pipettes were reusable. All were glass and were used, then washed and
replugged and autoclaved. Then plastic non reusable items came along.
However you can reuse TC flasks over and over if you want to save
money by washing plastic flasks and sterilise them for 3 minutes using
a microwave set on HIGH. The downside is that there is a increase the
chances of contamination.
Hope this is what you wanted to know
The following reference will be helpful.
Biotechniques. 1993 May;14(5):758-60.
A simple method for the reuse of polystyrene cell culture flasks.
by Shepard SR, Hartman JX.