Booms are good if you don't hit fences to often.
One day, we will have an indestructible boom... one day.
One downside is nozzles and bodies are their own design so it pays to keep some spares on hand if your dealer is not close.
I'm sure you know, hardi tips are a little bit of a 'shallower' square lug tip connection. If you have much easier access to other brands of tips, adapters might be a handy thing to have on hand. Either to throw an adapter with another tip on than wait a few days for a few replacements to come.
Definitely do this, nothing worse than having to buy $30 lids for a 2 second 'Oops'. I've literally talked to dozens of guys a year that lost lids either on their sprayers or when they are taking their empty water tanks on the highway. (Empty tanks have enough air in them to compress decently and pop the lids off if the the lids aren't too tight).
There are 'hinged' lids as well that if you lose yours once, you might forget again, so the lid just flips up and stays on. It also locks, just in case you have a neighbor that recently lost his lid

(It happens more than you think)
All in all, good luck to you!