There is no ideal age for every van. Mileage, reliability, repair bills, downtime and resale value matter more than the registration year alone.
Start with the job the van does
A van that spends every day on long motorway runs ages differently from one that covers short local routes. Look at annual mileage, payload, towing, stop-start work and how costly it would be if that vehicle were unavailable.
Watch the pattern of repairs
One repair does not make a van uneconomic. A pattern of faults, repeated workshop visits or difficulty obtaining parts is more significant. Keep a simple record of repair spend and days off the road.
Do not ignore resale value
Replacing before a vehicle becomes very difficult to sell can reduce the true cost of ownership. The right point varies by model, condition and market demand, so compare likely resale value with the cost of keeping it.
Review insurance at replacement time
Changing several vehicles can alter values, repair costs and the way the fleet is used. If you are replacing vans, it is sensible to make sure the existing fleet cover still reflects the business.