We have a Worcester greenstar junior combi boiler which, according to the paperwork we got from the previous owner of the house, was fitted in 2012. We had to get an engineer out early in 2016 to repressurise the expansion vessel as the cold pressure was below 1 bar but hot pressure up to over 2.5 bar. My other half noticed the cold pressure was low last week so topped it back up to just over 1 bar, today it's nearly down to the red when cold again which seems odd, but he also noticed the hot pressure was up on 2.5 bar again on Fri so I'm assuming it has vented some water via the PRV and the cause is that the expansion vessel needs repressuring again. Is it normal for that to need repressurising again in just three years?