That being said, three years may be a bit too seldom unless you're giving it a non-professional cleaning in the off years.
To answer OP: No. You've taken it upon yourself to clean instruments as part of your job instead of fighting for more budget so that it can be done professionally - that's 100% on you to do it. Why would they pay you for something you'd volunteer to do otherwise?
Just like writing your own drill book, it's a contracted service. If you do it yourself, don't expect to be able to get paid for it - you didn't bid the process out or contract someone else to do it.