Having said which you can write what you like in your log book - it only becomes a crime if you then use the untrue information for some purpose for which true information is required, such as a licence or rating issue or a job application.
Untrue.
If you have a fatal accident, the authoritoes will take your logbook(s) and check them. If you read accident reports they include information on experience gained from logbooks. A few reports contain information that logbooks have for example mistakes in the addition but overall, the accident investigation and as has been said the insurance will be based on a truthfull record of flying time.
Remember always that you only need to retain (or produce) the previous 2 years record. Anything beyond that is almost cast in stone unless you are applying for a licence.
Regards,
DFC