Right now there is no way to stop emission of a particle system without affecting particle emission rate per second and other things.
The only possible way is to use textures affecting emission density, but it't not stable as textures are not always sampled and if you use the particle system inside a link it's not working at all.
Allowing lifetime to be 0 we are effectively disabling emission without affecting the general aspect of the particle system.
It's a small patch that should not affect any other thing and should be stable.
I made it against the LTS branch, Blender-v2.83-release patch, with the expectation of this to be applied to 2.83 LTS.
AFAIK there is no other way to make this effect, collisions wont' work asn as I said textures are not stable and this will solve the problem of stop emitting without affecting the particle system in general.