How important is it to have hardened valve seats in a motor running unleaded fuel that is driven less than 1000 miles a year?

For instance if your heads are in otherwise good shape, but they are off the car would you ever consider adding the valve seats now or would you wait till you are having the heads rebuilt down the road?

if it matters motor is a 440 and heads are 906's

If it were me, I would consider putting some lead additave in the fuel and leave the seats stock.

If you're seeing limited mileage (2 to 3k) a year, don't bother w/ the hardened seats.

Well all I can tell you is that I have had a engine that I rebuilt in 1990 with stock leaded head seats and it is still running strong today!
I drag raced it some and mostly street drive it .
But I do use a lead substitute every other fill up on gas .I also use the Lucas fuel treatment and upper cylinder lubricant.
had the heads off and rechecked one time( in the time i have had it) They were givin a good bill of health by my machine shop .
I say if your heads are fresh then leave them alone but if you need a valve job then have hardened seats put in . Just depends on the use of the car if not drag racing every week then just stay stock . and use the additives.
To be honest if i ever need to have hardened seats put in because i burn a valve. Because of the cost I would buy a set of Edelbrock rpm heads.By the time you have all that machine work done the price with seats and every thing will probably be close or more than a better eddy head set up! Been there on other projects and used the out of the box eddys and never looked back put iron heads on the shelf for maybe some other use (doubt it !) lol.
You just can't believe the performance increase with the edelbrocks
engine is lighter , runs cooler , already for unleaded gas , compression bump with the small chambers = A+ in my book .

Over the years we have found that Mopar heads are much more tolerant of UL fuel than either of the brand x heads seem to be. That being the case I would not worry too much about it for limited driving .