Delayed Aircraft Deliveries on follow-up orders

I placed a follow-up order for 50 DC-9-50s and just realized that after delivery of the last aircraft of the previous order,  I have to wait almost 2 years until the deliveries continue. I have 150 DC-9-50s in the fleet already.

I had a similar problem before with a 767 order, but it was not that long until the deliveries restarted, if I recall correctly. Anyway the gap was way too long.

All planes were ordered (not leased) and I have plenty of cash.