An important part of any music is normally the duration of any specific note. It is therefore useful to retain control of the durations. If you're using a keyboard as a controller, this helps as most keyboards generate a Note On when the key is pressed, and a Note Off when the key is released. I take it that you cannot use such a controller, for some reason. So you start a note, then lose control of it.
Not sure if this applies to you, but mand devices may have some degree of polyphony, so they can play more than one note at once. Usually, there is some limit. If there is no explicit Note Off, notes may be still playing, and using up part of the polyphony, even if notes cannot be heard due to the envelope having reduced the sound. In due course, new notes will not be possible as the polyphony has been use up. Explicit Note Off will avoid this problem.
All Note Off could be used, but it would be a help to know how this works on your system. Does your system know which notes are playing, or does it need to check ALL notes to find the ones that are playing (even if not heard) to turn them OFF. This might be OK, but there might be too much time delay involved.
If you're using any sort of software, you could maintain your own list of Notes On, so you DO know which notes are On. Then you would know which notes to turn off. If you are generating the Note On via software, i.e. NOT using a keyboard) then you could create a duration as well, and automate the generation of a Note Off?.
Geoff