There is a common mistake people make around this issue. According to section 6(2) of the British Nationality Act 1981, the Spouse of British Citizens can naturalize in 3 years after living in the UK.
But the catch here is, the applicant must be “free from immigration time restriction” too (para 3 of schedule of BNA1981). The most common form of evidence to it is to possess the ILR status.
The ILR status is normally obtained after living in the UK for at least 60 months (Appendix FM of the Immigration Rules-E-ILRP1.3(1)). There is no concession given to a spouse of the British citizens to obtain ILR faster ( except a few exceptions).
THE ILR MOSTLY IS A 5 YEARS JOURNEY. SO THE 3 YEARS RESIDENCY REQUIREMENT FOR THE NATURALIZATION OF A SPOUSE OF BRITISH CITIZENS DOESN’T HELP.
There is a danger in making such a mistake of the premature naturalization application. It may lead to becoming an over-stayer. The loss of £1330 ( non-refundable application fee) would be painful too.
For a spouse of British citizens, the maximum number of absences would be counted for 3 years (not 5 years) only. It shall not exceed 270 days. This is the only benefit of 3 years route for the spouses of British citizens.