Not just that, if you consider it a benchmark you are very vulnerable to getting something similar to DGS (instead of a death grip where your cock is always expecting tightness, you will become unable to feel stroking sensations as well as you should and now always expect this fast movement).
Most CH videos are designed for wanking and not handy usage. Especialy noticed by very fast beats that you cannot reliable even thrust to. The best CH videos shouldnt exceed the speed you can normaly thrust in order to give a realistic intensity and avoid handy based DGS. Wanking is less intense than a sleeve as you cannot put your hand entirely around your cock all the time.
And yes, the handy can cause DGS, it doesnt have a case like a fleshlight, so its vulnerable to make it extra tight. Combining this tightness and speed is risky.
And this DGS (or HGS - as in handy grip syndrome) is worse than being unable to cum, as this can actualy cause you to go flacid during the action by lack of stimulation. While being unable to cum by overstimulation is possible (your brain being tired from processing it all - and usualy not a problem as often after a short rest you can still be brought over the edge), not even getting the stimulation at all is worse. Dont underestimate this, as its a lot more likely to cause it, rather than wanking (as at least in normal wanking you can get tired).
Even the handy speed is an issue, as stroke speed is often a compensation to get someone over the edge. Being used to this can prevent a women to bring you over the edge by stroking.
Being able to last a CH video of 30minutes on the handy without pause is a key sign of DGS. unless the CH video/script is designed to have a low pace or low distance strokes. Idealy over 80% of the CH script should be yellow or green in script player to make a 30min duration acceptable, more than that and the script is guaranteed to be overintense.
Vibrations are a bit of an exception here though, as wand usage during sex is actualy possible and can make things more intense. It will make the script red in scriptplayer even though the sensation will be diffirent. But that only works for short sections. Full vibration scripts will cause DGS quickly.
Being able to last 5min in a CH video is on that normal, and while your brain might stretch it to 7 minutes (basicly 2 songs), by that time its normal if you are close to the edge or already came.
A CH video designed to be mostly calm and involve ‘danger’ moments use this as their ‘danger’ moments are generaly just long enough to either get you close (edging), or to basicly force cumming. Its good they exist and that you lose during them. Its what would happen in normal sex when a women start stroking, trying to resist cumming there is what makes the cumshot more intense.
But note, there are cases where 2, or even 4h are doable: Milking machines. These machines are designed to keep the sensation this long, and even assist a bit there: suction keeps you hard, and the sleeve as they are very smooth dont provide overstimulation. As they never exceed a certain intensity (sure, it might look like they go realy fast - but keep in mind, this is significantly less intense than what a handy can provide), the moment a dom would take your dick out and starts stroking, that stroking is more intense already.
And just like that, a very slow handy video can on that provide a very long experience. Just like actual sex can also take over an hour.