Depends I like to have a reputable shop look at bearings every five years. Seen a guy last winter with two sleds and tire burned right up and right down to rim  on side of road too. Sand, dirt etc still can make its way in. Boat bearings are worst because of constant immersion into water.  you can jack it up and check for play and noise. If that checks out should be ok for another season. 5 year rule seems to work out for me and I do light towing. If you do for or five thousand kms a year might need to get them checked every 3 years.  They do spin pretty fast going down highway too. 

So not sure I understand what is being said here.   i have Dexter axles with the grease nipples and have read manual where it says to pump grease in while rotating the wheel slowly until clean or new looking grease comes out around grease fitting.  These are the hubs with the grease hole between inner bearing and inner seal.  Pump grease while rotating tire slowly watching grease come out around the grease fitting.     now maybe I am not that smart but if my hub pumps grease into the space between inner seal and bearing, grease travels through inner bearing then through outer bearing and then around grease fitting am I not okay?   Yes old spring loaded bearing buddies kept outer bearing only greased.   But if you have newer style axles with Dexter style hubs and a decent grease gun there should be no reason to go to a spring shop.   Or am I playing Russian Roulette?    

Do the 7’ wide clamshell style hybrids pull easier than the 7’ v-nose style that is higher with all other things being equal?  Curious if you’re better with less height, or if a v-nose is more aerodynamic.

I've got a 2020 HD 6.6 gas and a 2008 HD 6.0 gas. The 2020 has 120k and the 2008 is almost 400k No oil consumption has been noticed with the 6.6 and have been very happy with it so far. It gets better fuel milage then the 6.0 does which was a bit of a suprise as they have the same transmission. I'd have no problem getting a newer gas 6.6 with the 10spd. Towing the gooseneck fully loaded the power(14-16k) is there but so is the fuel usage lol

I like my hybrid 7x16 for the fuel economy.   That 1 foot lower makes a big difference