you should really declare this type of conviction for up to 11 years.
It is true that it shouldn't change the price once it's over 5 years, but some companies will ask for history for longer.
An example as to why they might do this is be because if you only had one DR10 or something similar it's not a problem but if you were a serial offender with numerous convictions then you might be seen as too high risk for that underwriter and they wouldn't cover you.
So yes 100% declare it coz chances are it won't affect it at all but if they need to know about it, it won't come back and bite you in the ass at a later date

hope this helps
Danny O
HIC