the guide lines that we follow say 25 years is the life span of normal twin and earth pvc cable as used in a house, a lot depends on how it is wired, usage (overloading),alterations made, and type of cable. a house built in 1965 will probably need rewiring as the lighting circuit will probably not be earthed(no requirement for earthing then) and if TT ( over head supply cables) it would be using the gas and water pipes for a main earth instead of an earth rod. also it will probably have a fusebox instead of consumer unit with RCD breakers, fuses were designed to melt before the cable (a 30 fusewire with 40amps flowing can take 1 hour to blow)to protect the cable where as RCD breakers are designed to turn off within about 50 milliseconds with a earth fault current of 30 milliamps so to protect the life of the occupants !

In short no. Modern PVC cables can last up to 70 years, provided that they were installed well and have not been altered and abused over the years. In general though the average life expectancy of house wiring is somewhere between 25 and 40 years.

Properties prior to 1967 are likely to have no earthing on the lighting circuits as this only came in in 1967, as such its likely that you will need to have the lighting circuits rewired if they are the original wiring from when the house was built.

Really the best thing to do it to get an Electrical Installation Condition Report carried out by a registered electrician (NICEIC or similar) and see what the report comes up with.

Its not uncommon for house built less than 20 years ago to need rewiring because the previous owners have done DIY alterations to the electrical wiring leaving it in an unsafe way.

Put a job here on mybuilder for an EICR and see what quotes you get. £100 is a fair price, but many charge more and others a bit less.

Really, the only way to be certain would be to get a qualified, registered (NAPIT, NICEIC, ELECSA, BSI) electrician to carry out an electrical installation condition survey which will provide you with the information you'd need to make a decision. The electrician will inspect and test the entire electrical installation (unless you want to restrict the scope) and provide you with a comprehensive report. Your electrician can then explain the report to you and discuss options for further work - if needed.

Prices will vary depending upon variables like the number of circuits; number of light fittings; number of socket outlets; number of outbuildings, garages, etc. You could probably reckon on spending £160 - £200 for the survey & report.

Hope that helps.
Martin