I’ve been using the Laser for a few years now.

If the car is in warranty, then change according to the schedule.

Out of warranty, check it regularly and change at 3% moisture or 5 years max.

Always use good quality fluid and flush through thoroughly (of course, you can never know how thorough the dealer has been, or even if they actually did it!!). I use Shell DoT 5.1, lower viscosity at low temps and long service life (my car has ESC and traction).

www.shell.com/content/dam/shell/static/chemicals/d...f

It would be interesting to test the water content of brake fluid from freshly-opened bottle, to two years and beyond, but it's probably largely academic.

DOT3/DOT4 fluids are reckoned to absorb moisture at about 2 to 3% per year at normal atmospheric pressures, and DOT4 is recommended to be changed when it gets to about 6%.

Although when young and stupid, and riding motorbikes, I have had some horrible old fluid in the braking system that's the colour of Coca-Cola and never had brake fade / fluid boiling problems. But that's not to say it can't happen.

Dealer says fluid needs changing every 2 years as per manufacturer......

Don't waste your money. The motor industry has a vested interest in creating as much work as possible and this is typical of the utter nonsense imposed on gullible drivers. Ask him/her which twenty first century 'manufacturer' of either cars or brake components advises such an absurdity. Even at 6% I doubt if you could get brake fade if you tried, unless you were driving down a steep Alp in an old Mini towing a heavy caravan. Even if you did, all you need do is pump the brake pedal to stop and then let eveything cool down.

The roads are full of ten year old cars, many of which have probably never had their brake fluid changed. Brake failure is virtually unheard of in these days of DOT4 brake fluid, well sealed reservoirs and well designed calipers.