Mains cylinder + expansion chamber. Good idea?

[miljee]

ie Not a Megaflo.
A plumber assures me that having a separate 'football shaped' expansion chamber near the cylinder is a better idea than an integral air bubble as you can service that far more easily. He reckons a Megaflo COULD need re-air bubbling every 5 months or so!

What do you think?

 

[ollski]

Takes 2 minutes to recharge an internal expansion.

 

[miljee]

My plumber reckons the external expansion tank system he's recommending takes 18-20 mins to replenish!..... to be fair, I can live with that IF it doesn't mean having to get a bloke out to replenish the air bubble every 6 months or so with sufficient useage.

I'm still not sure!