I think you are making a bit of confusion.
You are mixing the issue of "material" with the issue of how the material is placed in the rock.
Material: from which alloy the material is made. Either a bolt, or a glue in, if made from the same material, will show about the same issues with the general term of "corrosion". So do no expect if you use 304, 316, zinc plated any kind of difference between bolts and glue ins. Sure, there are some better "materials".
Bolts and glue-ins are offered in different materials.
If you buy bolts, yes, finding hangers in different materials can be difficult. You find they in 304, 316 and I do not know if Titts make anything "more resistant" to "corrosion.
Glue ins: you can find something from Titt made from materials that are supposed to resist corrosion better. In Sardinia given the smaller diameter of the rod, they found it "cuts" the resin, but I think these are discussion that starts at loads we will never achieve in the "real world". I have no detailed info about that.
Bolts: there are some bolts made from 1.4529 (HRC) from Hilti and a handfull of other reliable brands, that have a much better resistant to corrosion than ANY other glue ins available in the market
Most bolts producers are big companies that share liability for what they do. Some has certain certifications used for "working" business. No "climbing gear" equipment is a "big" company that have to share the burden of certifications (read it as "liability").
Glue: no glue supplier wants to deal with climbers, Because climbers has a very "everything goes" attitude, to write it down very simply. It's also a matter of cost. Every glue you buy, has no warranty. So if after a while is become chewing gun, it's your problem (equipper). I can tale some "problems" we faced with some glues of Hilti for example (just to name a very reliable company), that came out after 10 years (ten years) the glue was placed. I can tale you some things happened to my with 878 chartrides from Mungo (from CH)...
If everything goes ok, "glue ins" are the better choice for bolting. However, I have no clue if you have ever glued in a route (may be overhanging) and you'll deal with a great misery. Try.
It takes about 3 folds the time of bolting (or re bolting).
All other issues than removing glue ins, etc, etc, etc, are about the same systems you can use to remove a bolt. So where's the difference?
The 50 years that Titt is writing you about is exactly what the industrial (bolts) certification says. As I said, you are confusing the issues of "materials" and how they are placed in the rock. There are photos of glueins coming out for problems with the glue, and by corrosion, easily available in the web. Remind that if you place glue ins next to "tufas" you may consider "though some weakening from water has been observed with polyester".
Finally: I am a climber, I am a equipper and I sell gear. I try to keep in mind the 3 things I mentioned you.
I can tell my opinion.
Dealing with glueins, is a difficult task. It's a very slow procedure if you want to do it properly. Particularly if the rock is often overhanging (Kalymnos). In rebolting with glue ins, you should consider a labour cost of about 3, to four times, longer. Few people has the skills and attitude to do it "properly". Were some people starting to glueins, I will have my hairs go electric for the damage they may cause!
Dealing with bolts is faster, and the cases of bad bolts placed are "much lower".
Given the facts, I discourage the use of glueins. The chance to make it badly, it's MUCH higher, and the hassle to remove a glue in, try... I can also show you in Kalymnos some photos of poorly made glue ins, drilled too deep in the rock.
If people care about the rock, I instead suggest to bolt 12/100 mm HRC bolts (which, by the way, I do not sell) bought from the very handfull number of industrial supplies, and use a 12 mm 316/A4 hanger that one day, somebody will replace (only the hanger). This is probably the best +50 years solution. You should consider about 9/12 euro each point.
I am in Kalymnos 14-21 October if you want to share a beer. Of you can contact your fellow brit Alan Jarvis of UIAA technical team for further informaton.
Finally a very simple observation. Before removing any old bolts, I will test them some of them. There are some machines made to pull out bolts that it's worth considering.