There are some fairly complicated factors involved in determining whether your trailer is too long for easy towing with your rig. Things like truck's wheelbase, how far in back of truck's rear axle the attachment for the trailer is, distance between wheels on the axle, etc. I wish I had the URL for where I saw the tech. details. But one thing that I know from experience is that the longer-wheelbase your tow rig is, the better for towing, all other things being equal.
I have a sea kayak/canoe trailer that's almost 19 ft overall length, with an extremely long tongue. As the earlier poster said, having enough weight over the tongue makes for a smoother ride (but don't exceed trailer's OR hitch's tongue weight max). I used to tow a modified snowmobile trailer for about 10 years; that one had its advantages but its weight distribution was such that it bounced more than the new one.
Bearing Buddies is a brand name or model, and there are lots of imitations out there. The real ones supposedly are designed to be immersed in water IF they are adequately greased. I have them on the new trailer, and they allow easy lubing with a grease gun. But I don't drive the trailer right into the water anyway; it's not necessary with my boats.
Make sure the trailer is light enough you can hand-pull it on unpaved hills if that might be necessary. I have to hand-pull ours in a tight, uphill driveway-to-storage situation at home, and what is super-easy on flat pavement is barely doable on the unpaved, steep slope--especially with the trailer loaded. With the old snowmobile trailer (with a kayak on it), I had to get a running start and it was still a max-rep kind of action full of injury potential. That trailer weighed about 200 pounds more than my new trailer does.
Oh, yeah...a big ditto on the comment about not following other people's waving around for backing up. The only signal that I trust is STOP before reaching a rock or whatever.