I always check the rings on the gun (mounted to bases or rail). I use some alignment bars to spot check. Scopes are expensive so I feel that lapping is good insurance. I think that almost any setup could benefit from lapping or bedding. Is it necessary, not all time, you need to check it some how.
I put an expensive rail on a Rem 700, I put the screws into the back back hole and torqued it down at this point I tapped on the front of the rail, guess what I had a clicking sound letting me know I had a problem. If I had not checked and bedded the rail it would have a bow in it. This is just one reason I don't mount my scopes using a rail anymore.
On my last project I used a 20 MOA rail from a higher quality vendor on a Howa Mini. It didn't fit right. No idea if that was the rail being off, or the action being off. I epoxy bedded the rail to the action. I did one end at a time using an elastic clamp in the middle and only the screws in the end not being bedded not quite even snugged for alignment.
Had I just screwed it down, rings attached to that rail would have never lapped correctly. The only rings that would have worked with that unbedded rail would be the Burris rings with the spherical inserts. Might just give those a try on the next project.
You did not mention the action you are using. If it is a custom machined action with a quality steel rail, you do not need to bed the rail. If it is, say a Remington or Savage or etc. action, and an aluminum rail you need to bed the rail, making sure it is flat and square. Just my opinion.
I always test my rings by lapping just a little. If it shows even contact of more than 50%, I leave well enough alone. This has only happened once to me. In all the other times I have mounted a scope in rings (a couple dozen, I guess) the rings have always need significant lapping to get the contact area above 50%. I always bed my rails to the actions prior to mounting the rings and scopes. Even the high end rings tend to require some lapping.
Occurs to me, is it better to check the rings with a light lapping and risk ruining them, than it is to blind-faith install a scope and risk damaging it? I think so. Even at the lower end of decent scopes the rings still cost less by a large margin.