It really depends on the tape and how it was stored on sticky shed. I've been pretty lucky and have only one tape that I really liked that had that problem. It was a Phillips recording duplicated by Ampex in 1973. Actually, it was unopened when I bought it about a year and a half ago. I listened to it many times before it left a sticky mess all along the tape path. After several cleaning (with regular head cleaner) the deck was fine. I think with just about any older tape you'll get some oxide deposited on your heads the first couple of times you play it. After that, normal amounts of deposit will be found. For a while there, I was buying tapes hand over fist. I just had enough time to play them once, add leader, and give each one a quick grading for future reference. I was having to clean the heads after 5 or 6 tapes. Now, I clean them after 10-15 tapes and there's hardly any residue at that. I'm sure it was up to the different labels as to which tape they sprung for with their r2r editions. So even though Ampex duplicated for lot of them, they may not have all been getting the same tape spooled. Yeah,.. there were bean counters back then too.