Latest Linux distributions set fsck to check regularly your filesystems. This is certainly a good practice unless you restart often your pc and you have huge disks.

Each filesystem has many settings and one of them is "Maximum mount count". This defines how many times the filesystem can be mounted without being checked (with fsck).

By default Ubuntu sets this directive to 20. It can be checked with "tune2fs -l partition", for example:

root@a1:~# tune2fs -l /dev/sda3
tune2fs 1.40.2 (12-Jul-2007)
Filesystem volume name:   <none>
Last mounted on:          <not available>
Filesystem UUID:          c62badff-eb7c-408c-b1d9-4f3c13ce6df1
Filesystem magic number:  0xEF53
Filesystem revision #:    1 (dynamic)
Filesystem features:      has_journal resize_inode dir_index filetype needs_recovery sparse_super large_file
Filesystem flags:         signed directory hash
Default mount options:    (none)
Filesystem state:         clean
Errors behavior:          Continue
Filesystem OS type:       Linux
Inode count:              5865472
Block count:              11719417
Reserved block count:     585970
Free blocks:              1854261
Free inodes:              5828823
First block:              0
Block size:               4096
Fragment size:            4096
Reserved GDT blocks:      1021
Blocks per group:         32768
Fragments per group:      32768
Inodes per group:         16384
Inode blocks per group:   512
Filesystem created:       Fri Mar  7 22:24:47 2008
Last mount time:          Sun Apr 20 07:53:54 2008
Last write time:          Sun Apr 20 07:53:54 2008
Mount count:              17
Maximum mount count:      20
Last checked:             Wed Apr 16 08:53:02 2008
Check interval:           15552000 (6 months)
Next check after:         Mon Oct 13 08:53:02 2008
Reserved blocks uid:      0 (user root)
Reserved blocks gid:      0 (group root)
First inode:              11
Inode size:               128
Journal inode:            8
First orphan inode:       2540966
Default directory hash:   tea
Directory Hash Seed:      7643d333-c92b-4215-873c-1327792be2e9
Journal backup:           inode blocks

I have decided that this is too often and changed it to 30:

root@a1:~# tune2fs -c 30 /dev/sda3
tune2fs 1.40.2 (12-Jul-2007)
Setting maximal mount count to 30

Note that /dev/sda3 is my root filesystem.

Of course, you might decide to set it to a lower number if you have other concerns