snj979s and
hark (all-in-one reply),,
In my most humble opinion, the SB-600 is a great little flash unit. Over the years I've used mine on so many occasions that I cannot even begin to recall half of them, and I've had it for MANY years now (since I bought a new D300 wayyyy back - so you can get a feeling of how old it is). I don't do a lot of flash work but it has served me faithfully when I did. My current D750 is the 3rd camera it has served and I see no reason as to why I shouldn't keep using it. It does however, have its limits, as I found out recently in an event with huge open show-ground indoor arenas where you clearly need lighting assistance. The SB-600 didn't quite have the output to handle many shots, especially where you had to back up to get the total subject into the shot. As a result I went and bought a Godox V860II, which can easily take up the slack that the SB-600 leaves in certain areas, and it really is a fantastic flash.. That doesn't mean that I want or have to sell the SB-600. It now means I have two units to choose from, and the SB-600 will still be a first contender for indoor residential work, because I know its capabilities etc, so why spoil a potentially great shot when you already have the working knowledge of the flashes usage.. I wanted to buy an SB-910 but the cost was very high compared to the Godox which is less than half cost, and the V860II keeps impressing many users, so I took the easy way out, and now I can have my cake and eat it too - I saved many dollars and got an equally as good flash, maybe even slightly better..
As for regular maintenance,, that sounds like a good scheme, especially from the manufacturers point of view, keeping the unit going and guarding their products reputation etc, but that's something you the owner would have to weigh up. The only piece of advice I could offer here is - NEVER leave batteries in any appliance once the session is over, regardless of what the appliance is, a flashgun or a child's toy. There are so many crap batteries around now, even some so called reputable brands which are farmed out to other companies and countries for manufacture to keep costs down and as a result, several reputable brands are now little better than the el-cheapo stuff you can buy anywhere.. Over the years I have had too many of my battery powered electrical gadgets, from TV remotes to expensive radio equipment, virtually with their insides half eaten out because of leaking or defective batteries. Except for where long life is needed, such as a flash unit, I just buy and use any old cheap battery, most of which die young but sometimes they really hang in there and surprise me, being almost as good as the "better" brands.. I learned a long time ago not to leave batteries in the appliance once you've finished using it and I even check TV remotes regularly to make sure all is well...
Good luck with the camera's and flashes to the both of you...
Nikonitus