Date and time of each milestone:

Start: 1 --- 10 Jun 2012 12:37
1000 --- 10 Jun 21:43
2000 --- 11 Jun 04:36
3000 --- 12 Jun 02:07
4000 --- 12 Jun 20:08
5000 --- 13 Jun 05:21
6000 --- 14 Jun 01:19
7000 --- 14 Jun 09:45
8000 --- 15 Jun 03:02
9000 --- 15 Jun 21:32
10000 --- 16 Jun 15:42
11000 --- 17 Jun 22:26
12000 --- 19 Jun 01:52
13000 --- 21 Jun 06:10
14000 --- 29 Jun 05:47
15000 --- 7 Jul 04:13
16000 --- 14 Jul 23:32
17000 --- 21 Jul 02:13
18000 --- 22 Jul 04:05
19000 --- 24 Jul 13:41
20000 --- 26 Jul 22:47
21000 --- 29 Jul 20:21
22000 --- 4 Aug 16:45
23000 --- 17 Aug 04:20
24000 --- 1 Sep 02:54
25000 --- 21 Sep 03:04
26000 --- 19 Oct 17:53
27000 --- 30 Oct 20:24
28000 --- 3 Nov 06:17
29000 --- 11 Nov 06:32
30000 --- 18 Nov 20:49
31000 --- 28 Nov 04:12
32000 --- 12 Dec 23:01
33000 --- 15 Dec 03:17
34000 --- 19 Dec 22:24
35000 --- 1 Jan 2013 07:11
36000 --- 10 Jan 16:24
37000 --- 21 Jan 19:00
38000 --- 28 Jan 01:42
39000 --- 4 Feb 17:54
40000 --- 9 Feb 22:33

Time taken between each milestone:

1 - 1000 --- 9 hours 6 mins
1000 - 2000 --- 6 hours 53 mins
2000 - 3000 --- 21 hours 31 mins
3000 - 4000 --- 18 hours 1 min
4000 - 5000 --- 9 hours 13 mins
5000 - 6000 --- 19 hours 58 mins
6000 - 7000 --- 8 hours 26 mins
7000 - 8000 --- 17 hours 17 mins
8000 - 9000 --- 18 hours 30 mins
9000 - 10000 --- 18 hours 10 mins
10000 - 11000 --- 1 day 6 hours 44 mins
11000 - 12000 --- 1 day 3 hours 26 mins
12000 - 13000 --- 2 days 4 hours 18 mins
13000 - 14000 --- 7 days 23 hours 37 mins
14000 - 15000 --- 7 days 22 hours 26 mins
15000 - 16000 --- 7 days 19 hours 19 mins
16000 - 17000 --- 6 days 2 hours 41 mins
17000 - 18000 --- 1 day 1 hour 52 mins
18000 - 19000 --- 2 days 9 hours 36 mins
19000 - 20000 --- 2 days 9 hours 6 mins
20000 - 21000 --- 2 days 21 hours 34 mins
21000 - 22000 --- 5 days 20 hours 24 mins
22000 - 23000 --- 12 days 11 hours 35 mins
23000 - 24000 --- 14 days 22 hours 34 mins
24000 - 25000 --- 20 days 0 hours 10 mins
25000 - 26000 --- 28 days 14 hours 49 mins [CURRENT RECORD FOR LONGEST TIME]
26000 - 27000 --- 11 days 2 hours 31 mins
27000 - 28000 --- 3 days 9 hours 53 mins
28000 - 29000 --- 8 days 0 hours 15 mins
29000 - 30000 --- 7 days 14 hours 17 mins
30000 - 31000 --- 9 days 7 hours 23 mins
31000 - 32000 --- 14 days 18 hours 49 mins
32000 - 33000 --- 2 days 4 hours 16 mins
33000 - 34000 --- 4 days 19 hours 7 mins
34000 - 35000 --- 12 days 8 hours 47 mins
35000 - 36000 --- 9 days 9 hours 13 mins
36000 - 37000 --- 11 days 2 hours 36 mins
37000 - 38000 --- 6 days 6 hours 42 mins
38000 - 39000 --- 7 days 16 hours 12 mins
39000 - 40000 --- 5 days 4 hours 39 mins

Continued in Part 2