LH has a policy that crew in flights under 8h have to return within 24h (ie next flight back) and 8+h get 24-48h off. So TATL crew usually fly back the next day, anything east of the middle east gets 2-3 days off to recover. LH is unlikely to fly in FAs because others choose to stay longer. CCU and HYD crew are flown to DEL/MAA to return on other flights as working crew.

As far as the 742s go, they retired when the last of the 744s of the second order came in (2000-2002). Just like with the 346/333 delays that kept the unpopular ex-SN 332 and ex-NG 763 flying for LH, the 744s were slightly delayed and extended the life of the 742.

All 744 of the first order will start retiring with the 380 coming in (oh wait, those are running late too), the 744s of the second order will be ready to retire when the 748 is due to be delivered. LH is one of the wiser airlines when it comes to longhaul aircraft planning. All the US Airlines in BK are not ordering any new aircraft right now (except NW with a bunch of 787s and 333/2 coming in nicely to replace aging 744/742/DC10).

BOM with a 343? You got to be kidding. BOM is one of the highest loaded sectors. Anything under a 310Y config and they will have severe problems.

LH is simply not pulling 744s/343s out of service to refit seats unless C/D checks are required. For one the seat delivery schedule is tight and secondly they don't have any extra aircraft to play with.