There are a number of Home Office requirements that need to be met to keep your Indefinite Leave to Remain status. For example you are not allowed to spend more than 2 years outside the UK and you should consider the UK as your home. If you do not meet these requirements your Indefinite Leave to Remain status may be withdrawn.
A person with Indefinite Leave to Remain in the UK may be eligible to apply for naturalization as a British citizen.
How do I qualify for Indefinite Leave to Remain (Settlement)?
An Indefinite Leave to Remain applicant must have settled status in the UK. This usually means that you have been resident in the UK on the same visa class for at least five years (excluding student visas).
The only exception to this are periods of exceptionally Long Term UK Residency (10 years legal UK residency or 20+10 years as a combination of illegal and legal UK residency).
You and your spouse now also need to take and pass "Life in the UK" test. This test is obligatory since the 2nd April 2007. It will confirm that you and members of your family can speak English as well as know the life and history of the UK. This is a similar test that was previously required for naturalization applications only. You can now use the results of your test for naturalization applications, that is, you do not have to take the test again when you will be applying for naturalization as a British Citizen.