It does make sense, good question!
Here's some links I've found, seems like if you apply within 28 days of expiry they'll look upon you favourably!
1.
http://www.ukba.homeoffice.gov.uk/about ... youarrive/
We will consider any valid application to extend your visa, regardless of when you make it.
If you are applying for permanent residence, you will normally need to have been living in the United Kingdom for a specified length of time before you qualify. More information about the qualifying periods is available in the relevant sections of this website. You should not apply for permanent residence more than 28 days before the end of your qualifying period.
If your temporary permission to stay in the United Kingdom is due to expire before the end of your qualifying period for permanent residence, you will need to extend your visa before you apply for permanent residence.
2.
http://firstmigration.com/visas/uk/inde ... remain-ilr
We have received information that the UK Border Agency are looking at ways of stopping second Tier 1 extensions but no formal announcement has been about this yet
3.
http://firstmigration.com/visas/uk/inde ... remain-ilr
*Please note that you can technically apply for Indefinite Leave to Remain after 4 years and 11 months
Got an answer to my question btw?
http://www.immigrationboards.com/viewto ... ht=prorata