If you mean aerosol types such as Firemaster, First Alert, some Kidde models, Fireblitz and Jactone there are no servicing actions beyond user visual and user check weigh, with replacement at the end of the 5 year warranty.
Some of the other disposable/factory sealed types which in effect were non rechargeable versions of 'traditional' extinguishers such as those used in the past by Kidde & Guardian and gauged aerosols as used by Firemaster in the 80's/90's in theory can be subjected to the full Basic Service as you can remove pins and re-tag, gauge verify with a tool etc, the only difference being should recharge be needed or it's 5 years are up for Extended Service is has to be replaced.
I judge it on a model by model basis, most I come across are well past expiry so end up straight in the bin.
The ones with no maintenance possible are handy for vehicles and very small businesses as it's far cheaper to buy a new one every 5 years than have it serviced annually (which would cost more than the purchase price!)
Kidde have been misleading with some of their product aimed at the non commercial market as they label it maintenance free despite being standard commercial Gloria powder models which are fully subject to Basic & Extended services - some workplaces that bought these from B&Q and similar have got a nasty surprise when being written up for non maintenance of extinguishers as a result.