Gary I'm cutting/pasting from the other forum on this too,
I keep my K&C collection to about 70 sets, with perhaps 30 on display. I rotate them every few months so that all 70 sets are on display at various times of the year: a winter campaign diorama etc.
I don't get any enjoyment out of keeping things just for the sake of it, nor do I have the physical space to do so. In that regard I usually sell a few sets every few months to bring in new items to my collection. I've sold K&C's Alamo (AM and RTA), Arnhem (AN), Fallschirmjager (FJ), Russian (RA), Spanish American War (RR), Defence Work /Strong Point sets (SP), Vietnam (VN), Waffen SS - Winter (WS/W), The West (TW) and so on.
Whilst on some occasions it was like a dental extraction on others it was welcome to bring in new sets. On nearly every occasion the new sets have been vastly superior to that which went before them. Besides, these are not 1/72nd scale soldiers and vehicles that we are collecting: they take up a lot of money. However, principally the issue is one of space, and I'm at a stage in my life (33) where I need need the room for additions rather than having empty nests etc etc.
Some people like the hunt for a rare piece but then want to move on. Others love acquiring duplicates and triplicates of every figure and vehicle to the point of financial ruin. I think 2002 was probably a good time to become interested in K&C given the rise in quality and the general availability of many items - I came on board in 2003 - but I couldn't imagine still holding some of those sets I first bought back then. For example the WS12(W) and WS17(w) are crude, and the 'pyjama' effect of some of the camouflage does compare at all with what's currently on offer. However, I understand that many people want to complete their collection and I've no problem with that: in fact I'm the sort of person who puts a lot back into circulation in that regard. Equally it is true that K&C is continuously evolving, and yet revisiting similar themes - see the WS08, WS27 and WS58 patrols for comparison, or the WS09, WS31 and WS62 tank riders too. It is therefore nice to have in your collection an example of each era. But I'm still the sort of person who couldn't enjoy having a basement full of boxes whose contents get an outing once a year: I don't regard them as Christmas-type decorations and am therefore happy to buy in the new Battle of the Bulge and Fields of Battle and stand down some older WS and DD in the process.
Everyone has their own style of collecting. I don't think K&C could function without it. One interesting thing for K&C collectors is to keep an eye out on the K&C UK website for the new 'live auction' section. It'll operate like eBay but will obviously be a K&C-only auction site. It'll contain sets that K&C UK receive as trades for newer sets, as part of estate sales, former dealer stock surrender and so forth. As you're probably aware, K&C prices in Europe are about 30-40% higher than in the USA but if the auction site works it'll at least provide a means of returning into circulation many retired sets. Personally my fantasy would be the wooden Junkers Ju-52 (with a few FJ sets thrown in)!
Overall I'd be interested to hear of other people's collecting patterns, i.e. do the eBay prices tempt you to list a set of which you've a duplicate? Do you sell off to make room or to fund the acquisition of new purchases?
Certainly I'd recommend that newer K&C collectors focus on the spectacular quality of the currently-available sets and then just pick up the retired items they really want or which come reasonably priced.