Have a D5300 and just got a vivitar series 1 70-210 a big heavy Lens.... My stupid question is, do I need to worry about constantly supporting the lens while I have it on the camera? Like this lens seriously weighs more than the camera with kit lens.
Yes you should ... whenever you are shooting use your left hand underneath the lens to support it and manipulate the zoom/focus rings. If I have the lens vertical (pointing downwards) I just hold the body. If I'm walking with the lens/camera, I hold the lens near the body ... or cradle the lens/body in my arm that is held across my body. When I put the camera down, I make sure the lens is supported to take any stress off the mount. I totally agree with jaomul. Do not stress the lens/body mount.
Cant tell you what to do but I can tell you I mount my Tamron 70-200mm 2.8 VC (which is a pretty big and heavy lens) on my D3300 and I never support it, so far it takes it like a champ.
I have a 100-500 on D5300 and it does have the tripod mount on the lens but have never had a problem with the mount. I carry it holding the base of the lens where it meets the camera.
General hand-holding technique would have your left hand underneath the lens to operate the zoom and to turn the focusing ring. Second, a 70-210 Series 1 is a lightweight zoom lens compared to longer, heavier modern Nikon lenses like the 70-200 VR-II. Nikon does not build cameras that just snap at the lens mount from a little 1970's sized and weight zoom. Also, keep in mind that when a REALLY heavy lens, like a 300/2.8 or bigger is tripod-mounted it is the camera that hangs its weight on the LENS's mount. The camera can handle a fairly heavy lens without damage...Nikon has been building the F-mount since 1959...they kind of have an idea of how many screws are needed to anchor the lens mount to a camera body. I'm not suggesting you abuse the camera and go out and run a marathon while holding the camera by a right-hand grip only...but don't worry about a smallish zoom lens snapping the mount clean off...for that you'd need to drop the camera.
If you're talking about letting it dangle from a strap or a sling, I would worry more about banging it into something and damaging the body mount more than the weight itself causing any issues. That said, I'm not a rocket surgeon, so remember what you paid for my opinion.
I was thinking as Derrel says the 70-210 isn't really going to be a heavy lens (~0.7kg). It could have issues if used with a teleconverter or extension tubes, but thats more like to be failure of poorer quality fitting of the intermediate part. Over the years I've often had a Tamron 80-210 supported by the mount & neck strap, never any issues. Even having a camera & mid range zoom loose in the car during a motorway accident never caused any issue with the mount, despite a heafty blow ruining the lens. If you don't abuse it theres unlikely to be any issues. Supporting the lens while shooting is of course highly recomended, but I wouldn't worry much about the rest of the time with lenses under 1kg.
I was going to say, this lens doesn't look that substantial at all. It might weigh less than your camera, but that probably has more to do with your camera being light.
