Hello I have used many different types over the last 5 years and Its fair to say been soaked with spray, hail, rain etc on many occasions.
Crewsavers never misfired and went off when dave stepped off the boat in 6 metres no problem they were 18mths old at that point.
Sigma from Lalizas (who I sell) are about the cheapest jackets I have found, I always used them for a season and sold them, they have the reputation as being cheap no frills jackets but they are comfy, and in my experience very reliable, simple auto mechanisms, hidden by folds in jacket itself, we really abused them to the extent they got 400 hours use in 4 months. They also never misfired and again fired when we tried the most worn out ones after the year by leaping in!
Omega from lalizas a bit more refined both kids and adults all 195 newtons (mrked 150) all performed well but I found not as comfy as the basic sigmas.
Omega kids brilliant wellmade and well performing, had a client trip and fall in 2 metres fired V quick and chuffed client. ( I later sold all of these used at 4 months old on a rolling basis and one was bought by Daniel tD5 from this forum whose daughter fell in big time and who didn't get hair wet! ) despite the jacket being used and also 120 hours or so in use in some Vwet/heavy seas.
So we've used the market leader and the budget ranges plus one in the middle in all sorts of seas and never had any problems. I have sold many to other forum users and Noone has had an accidental auto firing.
I don't think theres a problem if you check them everyso often.