I submit the 30% that my insurance doesn't pay, because I prefer to purchase out of pocket from cpap.com, and submit to my insurance myself, because it's FAR LESS OF A HASSLE for me, than to use their "preferrred" brick and mortar DME. Someday, when I have nothing better to do, I'm going to send a scathing letter to Premera (my insurance) demanding that they enter the 21st century, and reimburse me 100% for those purchaes. But for now, I'm just going with it.
I also submit for reimbursement from my FSA when I purchase supplies that I don't necessarily submit to my insurance. Twice a year I make a big purchase of mask, hose, filters, chinstrap. That one I send to insurance and FSA. But if I find myself needing supplies in the meantime, often those just go to FSA. For example, I bought two used CPAP's, and needed filters for them that I didn't already have. So I bought filters off my twice yearly schedule.
Why twice a year only? Because I know they will pay it. I could probably submit more often, but frankly, I don't need to. My mask cannula lasts me about that long.
So, in short - YES!