From the screenshot I see the CPU load is no longer 99%?
I would be careful if it was to be close to 100% for extended periods of time because routers' CPUs often lack adequate cooling for the heat generated at such loads. Though you may check yours, maybe it has some sensors and maybe you could read them through I2C.
The ASUS RT-N66U there has 2 temp sensors, one on each of the transmitters, which actually don't shift from their usual 50 degC even when the CPU is at 99% load for 20 mins.
It only hits 99% occasionally once the initial block scan is done, usually it's 4% or so. The 'Load average' at the top there gives you the 5, 10 and 15 minute averages, where 1.00 is 100% load.
Just ran a test of 120 blocks at check level 4, which form
this post, means it includes the signature verification.
165952 2013-05-22 19:46:31 Bitcoin version v0.8.1.0-g34d62a8-beta ()
165953 2013-05-22 19:46:31 Using OpenSSL version OpenSSL 1.0.1e 11 Feb 2013
165954 2013-05-22 19:46:31 Default data directory /root/.bitcoin
165955 2013-05-22 19:46:31 Used data directory /mnt/Data/bitcoin
165956 2013-05-22 19:46:31 init message: Verifying wallet integrity...
165957 2013-05-22 19:46:31 dbenv.open LogDir=/mnt/Data/bitcoin/database ErrorFile=/mnt/Data/bitcoin/db.log
165958 2013-05-22 19:46:33 Bound to [::]:8333
165959 2013-05-22 19:46:33 Bound to 0.0.0.0:8333
165960 2013-05-22 19:46:33 init message: Loading block index...
165961 2013-05-22 19:46:33 Opening LevelDB in /mnt/Data/bitcoin/blocks/index
165962 2013-05-22 19:46:33 Opened LevelDB successfully
165963 2013-05-22 19:46:33 Opening LevelDB in /mnt/Data/bitcoin/chainstate
165964 2013-05-22 19:46:34 Opened LevelDB successfully
165965 2013-05-22 19:47:24 LoadBlockIndex(): last block file = 61
165966 2013-05-22 19:47:24 LoadBlockIndex(): last block file: CBlockFileInfo(blocks=789, size=129458329, heights=236623..237404, time=2013-05-17..2013-05-22)
165967 2013-05-22 19:47:24 LoadBlockIndex(): transaction index disabled
165968 2013-05-22 19:47:24 LoadBlockIndex(): hashBestChain=000000000000000dc4e0ec58b5d0f872f50ad0ee9f824c973e214911b8584bc5 height=237404 date=2013-05-22 19:32:57
165969 2013-05-22 19:47:24 init message: Verifying block database integrity...
165970 2013-05-22 19:47:24 Verifying last 120 blocks at level 4
165971 2013-05-22 20:35:20 No coin database inconsistencies in last 121 blocks (37183 transactions)
165972 2013-05-22 20:35:23 block index 2929699ms
165973 2013-05-22 20:35:23 init message: Loading wallet...
165974 2013-05-22 20:35:39 nFileVersion = 80100
165975 2013-05-22 20:35:39 wallet 16458ms
165976 2013-05-22 20:35:39 init message: Importing blocks from block database...
165977 2013-05-22 20:35:39 init message: Loading addresses...
165978 2013-05-22 20:35:40 Loaded 14691 addresses from peers.dat 633ms
165979 2013-05-22 20:35:40 mapBlockIndex.size() = 237412
165980 2013-05-22 20:35:40 nBestHeight = 237404
165981 2013-05-22 20:35:40 setKeyPool.size() = 101
165982 2013-05-22 20:35:40 mapWallet.size() = 0
165983 2013-05-22 20:35:40 mapAddressBook.size() = 1
165984 2013-05-22 20:35:40 init message: Done loading
165985 2013-05-22 20:35:40 ThreadRPCServer started
165986 2013-05-22 20:35:40 send version message: version 70001, blocks=237404, us=0.0.0.0:0, them=0.0.0.0:0, peer=127.0.0.1:0
So 48 min to fully verify 120 blocks. Not the worst...
P.S. At check level 2, 120 blocks just takes 3 mins. That's quite tolerable