Use of a long hose is not a problem. and can be a valuable tool. There are several considerations, first is hose routing this has many arguments. If you follow the teachings of several agencies theirs is the only way, and all others are wrong. You must find a technique that keeps the hose out of the way yet remains easy to deploy, each and every time. This can be by body wrap such as Hogarthian, or retention bands such as inner tube bands, as well as others. How you handle this will be determined by your equipment.
Next is the quality of your regulator and internal hose diameter. for as the hose gets longer your second stage may not perform as well, especially if you are using a cheap second stage. For the record my regulators are both the same.
We all should be using a rescue bottle when responding to a diver in trouble, this may be a pony that is passed off or a designated rescue bottle. On my personal rescue bottle I have a long hose, held for deployment with bands made from inner tubes. and only deploy what is needed. The bottom line is whatever configuration you chose requires practice until it becomes second nature.
Improper preparation will lead to problems, and failure to practice in all conditions will also lead to problems no matter what configuration you chose. For most PSD's they will not take the time to become proficient, with their equipment. If you care define why you are using or need a long hose, then practice those conditions that would cause it;s use and see if there is a better way if not you have your answer.
An example is a diver tangled zero vis. can't read gauges, deploy long hose as you cut your team mate lose. Or confined space exit such as from a car or van, the same benefit as for a cave diver. Just make sure you know why you are doing what you are doing.
Sincerely,
Bob Kinder
PSD Instructor, Cave Diver, Commercial Diver Supervisor