I defo think its a good idea.
With Max being FIV+ I do a 'basic' MOT every year, but this year asked to run bloods etc as I thought he'd been drinking a bit more recently.
Good job I did, his bloods were elevated showing early stages of kidney failure, a urine sample backed it up as being too dilute, so we have a change of diet now, with bloods due again next month to see if we need to medicate at all.
Forewarned is forearmed as they say, and if you catch problems early, they're much easier to try and treat.