A product much better than Armorall is 303 protectant. It used to be sold in small foil packets in some fly fishing catalogs just for the purpose you mention but I haven't seen it lately. White water rafters use it on their boats to protect against UV and to preserve the fabric. I buy it by the gallon(about$50-60) and use it on my RV roof,all the rubber and plastic on my vehicles both inside and out, my tractor seat, my Tote-N-Float and clean my fly rods and floating lines with it.I think you can do a search on 303 Protectant and come up with a web page that will fill you in on all of the details. Ive
first inspect it for cracking. If there are cracks, then the line is absorbing water and should be replaced. If its not cracked, forget the armor-all and go get the Umpqua Line Cleaner and Line Cleaner solution, then use that. Or for that matter any line cleaner is better than substitute stuff.
Armor-all is not for fly lines, it can damage them.