I don't consider 250 surface temp to be enough to heat except during shoulder season. For my house I need surface temp to be 400 or greater to hold the temps when it is less than 25 outside so I can see your frustration if that is all you are getting out of it for much of the time.
I don't know how large those 3 splits are but I don't expect much out of 3 of my splits after 4-5 hours. Right now I'm driving my stove pretty hard - I am loading it up full - 5-7 splits (depends on size of them, did 8 once when I had a few smaller ones on top of the pile). Starting with coals under the pile, I get stove top up to 550-600 within an hour of loading, then it will cruise between 500-550 for a couple hours, then begin to slide down to 400 range then settle down to 350-375 where I reload 5-6 hours later. I will increase air near the end there or in the middle, depending on when I'm around, anywhere after the temps start to slide down really. So in summary this is what my daily cycle roughly looks like:
Time (hours) / Surface Temp / Action & Comments
0 / 350ish / Level coals more to front less back, load full of splits (5-7 mostly) Engage cat once fully charred or 10 minutes
1 / 450-550 / Cooking along nicely, I may check temps to be sure flue isn't indicating it's getting 'too hot' - i.e. flue temp much over 300
1.5 / 575ish / Generally the leveling off temp range If flue temp is still over 300 and/or rising then I may adjust air down
3 / 550 / Sliding down from peak (slow slide)
4 / 500 / Sliding down still - Will generally increase air (to 2) in order to start burning coals away
5-6 / 350-375 / Final push to burn off coals - may open air more perhaps even open damper if necessary to get coals down, reload at this point.
Note that this pattern above is what I have settled on in the last couple days during the day (All temps are from memory and estimated, I need to log it sometime to be sure) - I seem to be loading 4 times a day - 6a/11a/5:30p/10p - overnight stove just burns down more without extra air to speed up the coal burn process.
I'm keeping my larger (not drafty) home comfortable in out temps (lows down as much as single digits, highs in 20s).
So - if you are interested in trying to figure out your situation, what is different? How large is your house?
What about your wood? Mine is all at least 2 years old (much of it is 3 or more) and what I have tested with the moisture meter has all measured less than 24%, most in the mid teens. I'm burning a mix of hardwoods - decent amount of quality woods like Hickory and Oak, but probably 1/3 is "Mystery meat" - oddball stuff that I can't identify.
The other thing is you may want to give the folks at Woodstock a call before giving up - they may be able to help figure out the issue.