I would not write on the sleeve while the negative is in it. Additionally I would wait until the writing is completely dry before reinserting the negative. However I have noticed bleed through after some years. It might be better to affix a paper label and write on that rather than directly on the plastic. For a number of years I used glassine holders and find them to be better. But of course you cannot print through them. Negatives tend to stick to the plastic after awhile but with glassine.