The new ones usually still have time, old ones on the market are generally fully booked. It also depends on the company philosophy. Friends of ours get their system installed 2-3 months after placing the order. The company has a large order in the neighboring town and uses smaller systems as gap fillers to bridge individual days, etc.
I commissioned our landscape gardener at the beginning of 2017, spread over 2 years 2018/2019. He does a lot of garden maintenance. Existing customers are not refused even if he only has to repot a flower. For him, new installations are gap fillers and the goal is to get more existing customers.