How long to keep records for - NOT immigration related

Now that I have been a British citizen for a while and no longer have to worry about proving how long I've lived in the UK or how long I've lived with my British husband, how long do I have to keep records for?

My file cabinet is getting full and messy.

Do I really need to keep things like bank statements that are over a year old?

What can I keep and what can I throw away?

sweet peach....
 I am one that wants to toss everything toss but keep everything as well (its an internal battle) so I go with the below

I keep anything tax related for 7 years...
House bills ect... after 1 year and no need for them toss them

Sign up for online access to all your credit cards or bank statement. No need to have paper copies of any of these bills as long as you diligently update your own electronic records (like download the CSV every year).

Keep yearly investment statements not the monthly (toss monthly at end of year)

Not sure what else you would keep as that sums up everything I have ;-)

I'd keep all immigration related paperwork. For example, when applying for courses, as I was born abroad, I still have to prove when I entered the UK despite being British.

Agree about the seven years for tax related paper work. Bills info I only keep a year's worth. 

I'd keep all immigration related paperwork. For example, when applying for courses, as I was born abroad, I still have to prove when I entered the UK despite being British.

I wasn't thinking about immigration stuff, but couldn't I just prove that by showing my American passport with the stamps in it?