Agree with all of the above, though my HA seeking 2019 is purposefully doing HF #1 with the three day break before Stanford #1 because of the fatigue factor. YMMV. We're taking the off days to see a few schools and visit friends.
The costs are high but between the two events, he will have a chance to be seen by each Ivy, several other HA Div 1's (ex: Davidson, Lafayette, Bucknell, Duke) and many HA D3's (ex: Amherst, Bates, Middlebury, MIT, Cal Tech, Chicago, Emory, Wash U.). But some schools, as you probably know, are only at one event. Example: Yale and Princeton are at HF #1 but not at Stanford. Dartmouth, Penn and Columbia are at Stanford but not at HF (not yet, anyway).
HA D3's at Stanford #1 but not at HF #1 (at least so far): Amherst, Claremont McKenna, and Trinity (TX).
I realize it's early for a 2019 for those types of schools, but he's 6'2" and he'd rather get seen sooner than later. My 2017 did not go to HF til Nov of 2015 in Florida, and things didn't heat up for him until July 2016, but he was less "projectable."
You might have more coverage if you wait til the July HF event, or even the August ones.