So is the cookie tin a good place to charge? Will PV turn off before batt is fully drained or will I need to keep eye on volts?
The problem with a cookie tin is that you will need to keep opening it to check on the status of the charge. The idea of it is to provide a "fire-proof" container if your batteries do suddenly go south while on the charger, but a cookie tin is probably not going to be strong enough to contain the heat in the case of a catastrophic vent. It
is better than nothing if you're concerned about "best practice" for charging, but I would suggest that a LiPo bag would be better in that case.
Best of all, though, would be buying a charger that actually stops charging once the battery is at 4.12 to 4.24 volts. Personally I recommend the Xtar WP2 II, as it has independent channels, can charge at 1 amp or 2 amps (1 amp would be your choice for protected 14500s, but 2 amps will charge IMRs and larger batteries much quicker) has over-voltage protection, reverse polarity protection and truly cuts the charge when the battery is full. It is the most inexpensive charger that offers these features, at approximately half the price of the nearest "competitor." The Nitecore Intellicharger looks to be a little better at very close to the same price, but I've read some tests that seem to disprove some of the claims so it's become a bit controversial. The Pila is considered the best, but at $45 I don't think it's worth twice the price of the Xtar. You do have to be careful, as a lot of chargers that claim to stop charging at 4.2 volts actually go into a trickle charge (like the Trustfire TR001). The Trustfire TR001, though, is one of the best chargers in its price-range and one of the most popular chargers on the market, so you'll be fine if you just want to stick with it. Just keep an eye on it while it's charging or buy an LiPO bag for the "safest practice." You should be fine just checking it every 30 minutes to an hour and taking the batteries out when they're done.
As far as discharging the batteries, protected Li-Ions have over-volt and under-volt protection. The over-voltage protection means that theoretically you don't have to worry about over-charging them as they'll "cut off" before they get over-charged. In this case everything I've written above is a "better safe than sorry" thing. The biggest advantage to them, in my opinion
*, is the under-voltage protection. The circuitry in the battery will cut itself off at somewhere around 3.2 to 3.5 volts. This means you mod will simply stop working
before the battery is damaged, so you really don't have to worry about it. In actual practice, though, the vapour production and taste will probably drop off enough that you want to change the batteries before they're fully drained anyway. So whether you vape 'til it stops or you change the battery according to the taste of your vapour, you don't have to worry about the battery drain.
With the set-up you're getting, you really don't have to worry much at all. The batteries themselves
should prevent over-charging (just don't leave them overnight) and they will definitely prevent over-discharging. The two things to keep in mind are that the initial charge
might take a fairly long time, and fully charged batteries of this type start at 4.1 to 4.2 volts (where an eGo generally starts at 3.7 volts) so you need to be prepared for more vapour and flavour than you're used to
* Another big advantage is that protected batteries will (almost always) cut off in the case of a dead-short. A dead-short is a case of the battery basically getting no resistance at all and "dumping" its entire charge very quickly. This is the vast majority a causes of catastrophic venting (what people mistaken call "exploding"). The problem is that it almost always cuts off by short circuiting before the battery can vent--which means you don't have catastrophic battery failure but you don't have a battery afterwards either. Very good for safety, can get kind of expensive. It is better to have to replace a battery than to have to go to the hospital, though
I hope this hasn't been too much all at once. Just remember that if you stick with protected batteries and atomizer/cartomizers that are 1.5 ohms or higher you really don't have anything to worry about.