The time it takes to get the reward is totally random.
My basis for saying this is:
DQ = Did Quest
Runned through the game 11 times,
First time: didn't do quest, didn't know but had Fragarach (kill Thrommel)
2nd time: DQ, after 6 days the couriers shoved up, normal reward.
3rd time: DQ, Knew swords, made party to fit (CG's) waited 32 days, mormal reward.
4th time : DQ, Same, but one CG, waited 13 days, normal reward.
5th time : DQ, TN party, with LN, CN, TN, Ng & NE PC's : 10 days
6th time : DQ, Pure CG party - i waited 45 days + special reward!
7th time : DQ, LG party - waited 2 days, got sword Homlet-E.Meadow. + special reward.
8th time

Q, LE party - destroy sword quest-still goth bonus by Killing Thrommel - waited over 2 months (60+ days)- lost count
9th time : DQ, The mges - N.Goods - still waiting - (over 90 days) - pending...
10th time : DQ, 5 Clerics-NG party Al-got sword at once (2nd/3rd trip)
!!th time : DQ, Solo Char - CG- Got sword after 8 days.
The strange is, each time i get the sword bonus i also get first 2000 PP, then some worthless medallions and a ring +1 for each PC and finally the sword.
But, with my pure CG party & my LG party i also got to chooce a magical item of choice. I chose a Pendant that increased caster level by +4 for Clerics, but it was broken.
Among others, i think i could choose +1 Arrows(20) or a ring +1 or +2, or an armor that was simply to weak.by then.(don't remember to clearly).
I didn't think to reload theese encounters since i was waiting for the Scather, but i think it has something to do with alignment.
Also note that my Solo PC (CG) didn't get extra items.
EDIT:
I remember now, thanks to Greywulf, the item i took was Necklace of Prayer Beads. The other items were the same as in Greywulf's post below.
EDIT END
Hope this sheds some light
