Twice in one night, I called an allin -- once with AA, once with KK -- late in tourneys. Both times I was even with allin player. In both cases, their hands were not as good as mine. (I didn't call AA with KK, for example.) Both hands lost.

pokerstars Hold'em No Limit - Level VIII (200/400) - 2006/10/27
Table 9-max Seat #5 is the button
Seat 1: Me (4999 in chips)
Seat 2: Player2 (5210 in chips)
Seat 4: Player3 (20510 in chips)
Seat 5: Player4 (7494 in chips)
Seat 6: Player5 (23394 in chips)
Seat 7: Player6 (6410 in chips)
Seat 8: Player7 (7955 in chips)
Seat 9: Player8 (6575 in chips)
Me: posts the ante 25
Player2: posts the ante 25
Player3: posts the ante 25
Player4: posts the ante 25
Player5: posts the ante 25
Player6: posts the ante 25
Player7: posts the ante 25
Player8: posts the ante 25
Player5: posts small blind 200
Player6: posts big blind 400
*** HOLE CARDS ***
Dealt to Me [Ks Kd]
Player7: folds
Player8: folds
Me: calls 400
Player2: raises 800 to 1200
Player3: folds
Player4: folds
Player5: folds
Player6: folds
Me: raises 3774 to 4974 and is all-in
Player2: calls 3774
*** FLOP *** [8h Jh 2d]
*** TURN *** [8h Jh 2d] [4s]
*** RIVER *** [8h Jh 2d 4s] [Qs]
*** SHOW DOWN ***
Me: shows [Ks Kd] (a pair of Kings)
Player2: shows [Qc Qh] (three of a kind, Queens)
Me said, "gg"
Player2 collected 10748 from pot
Player3 said, "ouchh"
*** SUMMARY ***
Total pot 10748 | Rake 0
Board [8h Jh 2d 4s Qs]
Seat 1: Me showed [Ks Kd] and lost with a pair of Kings
Seat 2: Player2 showed [Qc Qh] and won (10748) with three of a kind, Queens
Seat 4: Player3 folded before Flop (didn't bet)
Seat 5: Player4 (button) folded before Flop (didn't bet)
Seat 6: Player5 (small blind) folded before Flop
Seat 7: Player6 (big blind) folded before Flop
Seat 8: Player7 folded before Flop (didn't bet)
Seat 9: Player8 folded before Flop (didn't bet)

Here I have 120X BB in chips. Do I only call an allin when my stack is getting short?

In the other tourney, I called preflop with AA. The other player had KQs and hit a flush. If 1 fewer or 1 more flush card had hit, I would have won, because I had the flush ace.

PokerStars Hold'em No Limit - Level XIV (1500/3000) - 2006/10/27
Table 9-max Seat #2 is the button
Seat 1: Player1 (30373 in chips)
Seat 2: Me (10844 in chips)
Seat 3: Player2 (8325 in chips)
Seat 4: Player3 (18954 in chips)
Seat 5: Player4 (22375 in chips)
Seat 6: Player5 (52253 in chips)
Seat 7: Player6 (14766 in chips)
Seat 8: Player7 (16504 in chips)
Seat 9: Player8 (7067 in chips)
Player1: posts the ante 150
Me: posts the ante 150
Player2: posts the ante 150
Player3: posts the ante 150
Player4: posts the ante 150
Player5: posts the ante 150
Player6: posts the ante 150
Player7: posts the ante 150
Player8: posts the ante 150
Player2: posts small blind 1500
Player3: posts big blind 3000
*** HOLE CARDS ***
Dealt to Me [Ac Ad]
Player4: folds
Player5: folds
Player6: folds
Player7: folds
Player8: folds
Player1: raises 6000 to 9000
Me: raises 1694 to 10694 and is all-in
Player2: folds
Player3: folds
Player1: calls 1694
*** FLOP *** [As Qs 6d]
*** TURN *** [As Qs 6d] [2d]
*** RIVER *** [As Qs 6d 2d] [Td]
*** SHOW DOWN ***
Player1: shows [Kd Qd] (a flush, King high)
Me: shows [Ac Ad] (three of a kind, Aces)
Player1 collected 27238 from pot
*** SUMMARY ***
Total pot 27238 | Rake 0
Board [As Qs 6d 2d Td]
Seat 1: Player1 showed [Kd Qd] and won (27238) with a flush, King high
Seat 2: Me (button) showed [Ac Ad] and lost with three of a kind, Aces
Seat 3: Player2 (small blind) folded before Flop
Seat 4: Player3 (big blind) folded before Flop
Seat 5: Player4 folded before Flop (didn't bet)
Seat 6: Player5 folded before Flop (didn't bet)
Seat 7: Player6 folded before Flop (didn't bet)
Seat 8: Player7 folded before Flop (didn't bet)
Seat 9: Player8 folded before Flop (didn't bet)

Here though I have chips, the blinds are so large that I have just more than 3X BB. Had I gone allin postflop, the trip aces on the flop probably would made me even more eager to push.

Should I be playing these big pairs first in only and leaving the calling of allins to someone else -- maybe someone with more chips?