They're fine. Be aware that they usually have a max capacity of around 2000maH. I find that is plenty.

Some rechargeable batteries can lose their charge in as little as 2 weeks if not used.

For that reason, I switched to Sanyo Eneloop batteries. They retain up to 80% of their charge after 12 months.

Yes, they are similar to Chinese meals.

Once you've had one, soon after, you'll want another.

I don't know how far South that this phenomenon can be seen but I think you have to be way up in the North of Scandinavia, Canada, Greenland, Iceland, Arctic etc. or similar cooooooold place.

Are you planning a trip to one of these places?

No I don't, but others here do. Maybe some will comment later. I think Clarky has one, but I'm not sure.

The pistol grip is a sound idea but I'm happy with a ball head.

I believe there is a very good pistol grip made by Slik. I personally wouldn't buy anything other than Manfrotto for the reason I stated previously.

No, but the only advice I can give is . . . stick with one manufacturer. I've settled on Manfrotto gear, mainly because I hate changing those base plates. Consequently, mine are all the same, and every piece of kit I have that needs one, has a base plate fitted.

or even the 50-200mm ? ? ?

The focussing capabilities of the SDM equipped lenses is far superior (faster) than the older screw drive lenses. I'd suggest you start saving your pennies

Which lens do you have?

You already have a pretty good all-rounder lens in the 18-250mm.

My advice is to wait, use what you have, then decide which focal length you might want to use.

For lanscape, architecture, or building interiors, the Sigma 10-20mm or the Pentax 12-24mm would be a good choice.

For longer focal lengths, consider a good quality teleconverter (T/C). I can personally recommend the SMC Pentax-F 1.7X AF T/C. The main advantage of using a T/C to extend the length of the lens you have is weight. Another long lens will be reasonably heavy, a T/C would add minimal weight, but increase versatility.