The way things stand at present you will do time at sea as part of initial officer training and specialist logs officer training at ILOC. After that you can expect 1 x tour (18 months) onboard as a SLt of Lt (Deputy LO on a frigate or destroyer or alternatively LO on a submarine). On promotion to Lt Cdr you will then do a further 18 month or so job as the LO on a frigate or destroyer. In between all of that there are various Optour type roles in the middle east/ elsewhere (6 or 9 months in duration), but with the drawdown from Afghanistan these are getting few and far between.
Time onboard ship does not necessarily equate to time away (for example the ship might be in refit/maintenance alongside) but we have so few ships nowadays that even if you arent on the other side of the world, you could find yourself at sea off the UK coast (and usually, and irritatingly, outside of mobile range!)
Bu tcompared to (say) warfare officer, the logs branch is relatively stable in terms of time away.
