I have used yellow sleeves for years including LED'S. Never had a problem, Never thought about it being a problem and never will be a problem. Pop them on and get onto making money screen printing
Rick, just because it was not a problem for you, it does not mean such is the case for the others. If the screens in a storage room are exposed to UV, they will be partially exposed and they will vary in how much time they need for full exposure, will have problems holding repeatable dots and in general be pretty unpredictable. We are talking minor variances, but enough to cause real problems.
No question about it, do a coin test as suggested by Dave.
Pierre