A lot of boats were never bonded by the manufacture. Mines a 1976 model, not bonded and permanently moored in saltwater with shore power running a smart charger full time.
I'm in the PNW, two zincs on both shafts and one on each rudder and they last a full boating season and I've never had any electrolysis on bronze thru hulls, which are not bonded. If it was originally bonded, then I would leave it. If not bonded and you're having no problems then leave it un-bonded.
Careful . . .I Have a Generator and I'm not afraid to use it !