Respawning Mammoths?

[Sines]

Is there anywhere I can find respawning Mammoths for an endless supply of Grand Souls? I avoided getting the Black Star, but since there's basically no penalty for getting it and using it, I'm starting to regret the choice. I might just use the console to swap out my regular Azura's Star if Mammoths are a limited (or at least unreliably appearing) resource.

Alternatively, any reliable, renewable source of Grand Souls is acceptable.

EDIT: On a related note, if you drink a potion for better Enchantments, does it last for the whole duration of your time in the Enchanting Table window, or are you in a bit of a race against the clock to select your options and name your gear?

[HiTmAn]

black star is much more power cz any creature u soul trap will be maxed..

[Quail]

I tested the time affects from a fortify enchanting potions in which the results were that the clock keeps ticking even while you are in the enchanting menu. That would make it a race against the clock.

As for the mammoths respawning I have an excerpt from a steam thread
--
1) Go to an external area with enemies (I used Silent Moons Camp)

2) Kill the enemies and fast travel to another cell (I went to Whiterun)

3) Wait for 2 days and make a new save

4) Return to the area; the bodies should be gone, and at this point no amount of waiting will get them to respawn in my games

5) Reload the second save and wait for 8 more days

6) Return to the area after the total 10 day period and the enemies should have respawned normally

Link to steam thread
http://forums.steampowered.com/forums/showthread.php?t=3208704
--

Other NPC's that have grand souls include:
Humanoids
Corrupted Shade
Daedra
Dragon Priest
Draugr Death Overlord
Falmer Warmonger
Guardian Saerek
Guardian Torsten
Riekling Charger

Soul gems
http://elderscrolls.wikia.com/wiki/Soul_Gem_(Skyrim)

[Vrakos Anthrakir]

@the edited in related note,
it's a race against time, the potion description literally says how long it lasts