Helieng, there are two answers to your original question.
Firstly, emergency pop out floats are just that. For use in emergency to keep the helicopter afloat for long enough to enable the pax and crew to exit. Generally speaking (as there are many different types of installation) you should expect the helicopter to stay afloat for approx 20-30 mins, in clam water's. Acouple of minutes in rough water's. If the ditching has occurred near to the beach, a vessel or offshore installation then you may just have enough time to recover the aircraft.
The pop out floats have a nasty habit of slowly deflating. Hoses, connections and the floats themselves slowly leak after being inflated. The air bottles used to inflate them have one shot of air to inflate once. Usually one float will deflate faster than the others (due to Murphy’s law) and cause the aircraft to list or even roll over.
Great care has to be taken when alighting the water with regard to forward, sideways speed and wave action to ensure one is not ripped off. See above for outcome. All this at a time when the excrement has already hit the air-conditioning.
The second answer to your question is with regard to fixed floats as per the R22 Mariner. These are either of a rigid plastic or rubber construction or inflatable (with the ability to top up the inflation). Fixed floats are designed to be in constant use for many take off's and landings. Great fun at start up, trying to keep the yaw under control. Great fun taxying (although not recommended). I don't know of any twin machines using fixed floats (I stand to be corrected) but reasonably popular with single machines, B206, H500, H300, R22 etc. Used extensively by Tuna spotters.