It is perhaps only condescending/patronising if you take the attitude that you know better. The answers you were given were good ones - whether or not they are what you want to hear.
Perhaps some of those people that are responsible are fed up seeing idiots attempting to learn technical diving off the Internet and subsequently filling up recompression chambers? Some of those idiots came to technical diving because they were not comfortable doing long deco hangs...it is sort of the antithesis of the technical attitude where you use the techniques to get what you want out of a risky dive with the minimum of risk. I decide on my bottom time and then do the deco it requires.
I was doing the air times for a few years before venturing outside BSAC for Nitrox and technical training 12 years ago. I have been a bit of a Nitrox evangelist ever since.
Well let's see what I can do then. Very roughly speaking 30mins at 30m to 50m on air + 80% or higher - deco times will approximate bottom times. Obviously it depends on the exact depth and time the longer and/or deeper the more deco and at 50m for an hour I might spend 90mins (150% of bottom time) decompressing . You can usually make it out the water faster on BSAC 88s if the profile is not off the end of the table.
Nitrox tables (other than 88s) and accelerated deco tables are based on EAD extrapolation. It is more theory than experiment so most people use a conservative (compared to 88s) table based, to one extent or other, on Buhlmann's. Even so very few people stick exactly to the table they have chosen and will alter their profiles according to their gut feelings. It is very difficult to say what is or is not correct because the statistical verification models just do not exist. If this worries you, you probably should not be technical diving.
Anything over 75% will keep your PPO above 1 for the bulk of decompression. As shallow stop times increase the greater the difference this makes. For short stops there will be virtualy no significant difference over backgas or 50%. It takes time for accelerated deco to do it's stuff. Personally I don't bother accelerating any less than 30 minutes of air stops, about 15 mins on 80%, but I do the air stops up to 15 mins on 80%.
There are a number of cons when it comes to using 100%, CNS exposure rises significantly and heavy sea states can make a 6m MOD very uncomfortable. With 80% the gas switch is out the way before ascending into the surf zone in any remotely divable conditions. 100% offers little theoretical time advantage over 80%. It has the advantages of being devoid of Nitrogen and the treatment gas for DCI.
A basic rule of accelerating decompression is being prepared to do the air stops in case you lose access to the deco gas. Personlly I do not think it is enough to assume you can do the longer stop times, you should try them and be comfortable with them.
Ideally you would be using a Nitrox backgas to extend the bottom time at 30m to 35m but yes it can get expensive. Using 50% to decompress from your 30min 30m air dives, according to the air tables, will cost similar to accelerating deeper/longer dives. What is likely to change is how you feel after the dive. Only you can say if it is worth it, but it stands a chance that if you do not think so you are not going to find much use for accelerated deco.
Once you start extending times well beyond no stop times a lot of additional risks come into play. DCI is quite a small one. DCI is however almost inevitable if you run into the consequence of those other risks. The worse possible scenario is having to surface with the equivalent of a massive backgas decompression obligation because you fell prey to one of the other risks. Hence technical diving tends to favour those who are adventurous in their objectives and conservative in their plans.
