Why does my MacBook Pro take so long to go to sleep?

Question

Until recently, when I pressed Option-Cmd-Eject, my MacBook Pro used to go to sleep almost immediately (e.g. within three or four seconds). It's a MBP 8,2 with an SSD and 8GB RAM.

Since a week or so, it takes much longer; around fifteen seconds or even more. Here's the console output from pressing the keyboard shortcut until the kernel's sleep message:

7/31/11 11:50:59 PM mDNSResponder[17]   Client application bug: DNSServiceResolve(charon._smb._tcp.local.) active for over two minutes. This places considerable burden on the network.
7/31/11 11:50:59 PM mDNSResponder[17]   Client application bug: DNSServiceResolve(Meredith(SSH)._ssh._tcp.local.) active for over two minutes. This places considerable burden on the network.
7/31/11 11:51:03 PM kernel  PM notification timeout (pid 3715, Google Chrome He)
7/31/11 11:51:03 PM kernel  hibernate image path: /var/vm/sleepimage
7/31/11 11:51:03 PM kernel  sizeof(IOHibernateImageHeader) == 512
7/31/11 11:51:03 PM kernel  Opened file /var/vm/sleepimage, size 8589934592, partition base 0xc805000, maxio 400000 ssd 1
7/31/11 11:51:03 PM kernel  hibernate image major 14, minor 2, blocksize 512, pollers 5
7/31/11 11:51:03 PM kernel  hibernate_alloc_pages flags 00000000, gobbling 0 pages
7/31/11 11:51:03 PM kernel  hibernate_setup(0) took 0 ms
7/31/11 11:51:06 PM kernel  IOThunderboltSwitch::i2cWriteDWord - status = 0xe00002ed
7/31/11 11:51:06 PM kernel  System SafeSleep
7/31/11 11:51:15 PM kernel  IOThunderboltSwitch::i2cWriteDWord - status = 0x00000000
7/31/11 11:51:15 PM kernel  hibernate_page_list_setall start 0xffffff809225b000, 0xffffff809229b000
7/31/11 11:51:15 PM kernel  hibernate_page_list_setall time: 447 ms
7/31/11 11:51:15 PM kernel  pages 1564968, wire 250981, act 375476, inact 548, spec 267, zf 6140, throt 0, could discard act 115301 inact 538951 purgeable 39710 spec 237594
7/31/11 11:51:15 PM kernel  hibernate_page_list_setall found pageCount 633412
7/31/11 11:51:15 PM kernel  IOHibernatePollerOpen, ml_get_interrupts_enabled 0
7/31/11 11:51:15 PM kernel  IOHibernatePollerOpen(0)
7/31/11 11:51:15 PM kernel  writing 631584 pages
7/31/11 11:51:15 PM kernel  encryptStart 69aa50
7/31/11 11:51:15 PM kernel  encryptEnd 89ade70
7/31/11 11:51:15 PM kernel  image1Size 310265344, encryptStart1 69aa50, End1 89ade70
7/31/11 11:51:15 PM kernel  encryptStart 127e4600
7/31/11 11:51:15 PM kernel  encryptEnd 40c9f7c0
7/31/11 11:51:15 PM kernel  PMStats: Hibernate write took 8066 ms
7/31/11 11:51:15 PM kernel  all time: 8066 ms, comp time: 2645 ms, deco time: 0 ms, 
7/31/11 11:51:15 PM kernel  image 1086978048, uncompressed 2587336704 (631674), compressed 1074427632 (41%), sum1 4849c5df, sum2 d1708974
7/31/11 11:51:15 PM kernel  wired_pages_encrypted 146094, wired_pages_clear 103149, dirty_pages_encrypted 382431
7/31/11 11:51:15 PM kernel  hibernate_write_image done(0)
7/31/11 11:51:15 PM kernel  sleep

Note that I am aware of this question, but I haven't changed anything in the system and it used to go to sleep faster than now. Considering that PMStats reports a hibernation write time of over eight seconds, this leads me into thinking it is the RAM content.

The only system changes I remember are installing the two updates for 10.6 that came out just before Lion's final release. Did that change anything?

How would I go about troubleshooting this?

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Even after

sudo pmset -a hibernatemode 0
sudo pmset -a hibernatemode 1

it takes roughly the same time to sleep.

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FYI, here's the information from a "clean" (non-safe) sleep:

8/1/11 2:26:49 PM   kernel  AirPort: Link Down on en1. Reason 8 (Disassociated because station leaving).
8/1/11 2:26:50 PM   kernel  IOThunderboltSwitch::i2cWriteDWord - status = 0xe00002ed
8/1/11 2:26:50 PM   kernel  IOThunderboltSwitch::i2cWriteDWord - status = 0x00000000
8/1/11 2:26:50 PM   kernel  IOThunderboltSwitch::i2cWriteDWord - status = 0xe00002ed
8/1/11 2:26:50 PM   kernel  IOThunderboltSwitch::i2cWriteDWord - status = 0xe00002ed
8/1/11 2:26:50 PM   configd[14] network configuration changed.
8/1/11 2:26:50 PM   kernel  System Sleep
8/1/11 2:26:50 PM   kernel  IOThunderboltSwitch::i2cWriteDWord - status = 0x00000000
8/1/11 2:26:50 PM   configd[14] network configuration changed.
8/1/11 2:26:50 PM   kernel  IOThunderboltSwitch::i2cWriteDWord - status = 0xe00002ed
8/1/11 2:26:50 PM   configd[14] setting hostname to "charon.local"
8/1/11 2:26:50 PM   kernel  IOThunderboltSwitch::i2cWriteDWord - status = 0xe00002ed
8/1/11 2:26:50 PM   kernel  IOThunderboltSwitch::i2cWriteDWord - status = 0xe00002ed
8/1/11 2:26:58 PM   kernel  Wake reason = EHC2
8/1/11 2:26:58 PM   kernel  System Wake