When cleaning up recordings that are in danger of deteriorating - tapes, cassettes etc., try and keep two digitised copies, one unedited and one for present use.
Alan Day is perfectly correct in saying that any editing can affect the quality of the sound, even on the most expensive (Cedar?) equipment, but with the advance of technology, it may well be that in the not-to-distant future this will not be the case and you may do irreparable damage to precious recordings by editing them.
I agree with those who have suggested that recordings that are rare, important and of general interest, should be donated (copies) to an archive (the "if the bomb drops philosophy). We were lucky enough to be able to donate copies of our field recordings to The National Sound Archive at The British Library, The Irish Folklore Department (Dublin) and The Irish Traditional Music Archive, so if our house burns down tomorrow................
My heart went out to the man who spent hours recording the legendary fiddle player Padraig O'Keefe,and, realising their importance, carefully stored them in a metal box in a cupboard, only to find that when he opened the box all the coating had stripped off the tapes because he hadn't noticed a hot water pipe that ran through the cupboard.
Jim Carroll