RTTR, good RCR123's such as AW's in my opinion, are not as likely to "vent with flame" as a primary lithium cell. That doesn't mean it can't happen, but it's very unlikely if you follow the rules, as others have suggested. There are far more instances of lithium primaries "venting with flame" on the Forum, than Li-Ion cells.
I read that you should try to always avoid fully discharging AW RCR123's or any rechargable. Does that mean I need to time my flashlight usage and pull the cells at 50-70% discharge? It would be a real pain to have to pull out the volt meter to check them during use.
What you read is true. Li-Ion cells take a little more effort to maintain and use properly. The trade off is superior performance.
It's not as hard as it seems to prevent over discharging/discharging until the protection circuit trips. Once you become familiar with a light, you know about how long it runs, without a stop watch. It's pretty easy to gauge how much you use it, and charge/change cells before you run them down too far. If your light runs about an hour, try to charge the cell(s) when you think your 3/4 of the way there.
Also, keep in mind that Li-Ion cells can be recharged at any time, without any penalty. This alone helps prevent over discharging. If you run your light 10 minutes at a time, charge the cell(s) every two or three uses. That way, in the above example, you'll have a good reserve, if needed.
One thing I personally don't do, take the above example, a light that runs for one hour, I don't run it 5 minutes and then charge the cells. I aim for the most part, to run the cells down about halfway before charging. This strategy is less of a chore, and still gives me a 1/2 hour reserve, if I need it. Also bear in mind that Li-Ion cells suffer the least internal degradation when they are about half charged.
As far as checking the voltage of your cells, that is something that goes with Li-Ion cell usage. It is a good idea and keeps you abreast of the cells performance and condition. This is much more important with Li-Ions than other chemistry cells, and just goes with the territory.
Dave