AFAIK there are two types of wheel spacer.
The ones to avoid use a screw-on extension piece on each or your existing wheel studs then a spacer ring which slips over these extensions. These seem to be known for giving problems.
The other type goes straight on your existing studs and provide a new set of studs to secure the wheel - if these are of reasonable quality they don't seem to suffer from the same problems.
If you use spacers to alter the effective offset of your wheels from the stock set-up, then you'll probably need to check, adjust and replace your wheelbearings more often. I'd imagine the further you go from stock the shorter the life of your bearings, all other things being equal.
I know Ian is using 30mm spacers to correct the 28mm positive offset Hilux rims on his car to (almost) match the zero offset spec for an 80.
To the OP: I'd avoid using spacers without a specific need to do so.
To Ben: I'd check your wheel bearings regularly with your nice looking new rims.
All the best,
Toby
1990 HDJ80
1994 HDJ80