I often ride offshore, and indeed the pleasure is great but risky ;To me there is no absolute answer to this question , as there are show stoppers like for example :
- your site : offshore current
- wind previsions : high wind variation expected (including drop of wind)
- thermical risk : cold water and/or no good wet suit
- site fragmentation (other kiters, safety or tourists or fisherman, VHF or mobile network)
- your physical conditions and your swimming skills obviously
- your equipment (board amovible leash, lifejacket, watertight backbag with mobile phone and urgency number already recorded, whistle, little flippers, sometimes a marine VHF); all in all it does not distrub the ride, franckly
Of course it is your own decision to increase the risk, but my point is that for example hydrofoiling in light offshore wind without current in summer breeze with 2 other aware kiters is feasible without taking too much risks and even without backbag IMO (but I agree we never know, but also for onshore winds with obstacles in the beach for example);
Personally I ride in a frequented area, rarely alone when off, so we are riding offshore with 1 or 2 collegues even in the winter ; in that case I have a mobile phone with me, good thermical protection with gloves, in the morning in the week-end to maximize the chance to get help from a tourist of fisherman boat. But I must say I had one or two bad surprised (with side-off current) for which the safety described above where or were close to become useful (mobile, flippers, LEI for its flotation and better visibility from distance).
All in all, it will depend on your motivation for riding vs the risk your are ready to take: kitesurf is always risky more or less , offshore is just an increase of it , like doing big jumps close to the beach is ...