Canvas is great on a boat, usually waterproof, UV resistant, strong and long lasting, Sunbrella even guarantee  their canvas for 10 years so long as it is looked after.
Looking after it is easy, a fresh water soapy wash, make sure that it is tied down and not flapping in the breeze, and be gentle on the zips. Depending on the stitching thread and the environment it is in, the canvas could need re stitching every now and then.
Once though it is gone, it is gone, don't try and get those extra few years out of it as you will only do more damage to whatever it is supposed to be protecting.
I have just cleaned a mainsail that has been under a canvas cover which should have been replaced years ago. Firstly it leaked so the sail was always wet, thus moldy, and secondly as the canvas broke down the colour rubbed itself all over the sail, a nice tinge of green which does not come off is the result.
The sail now also has wear marks where it was rubbing too.
Your trimmer/sailmaker will tell you if your canvas has more years left in it, or bring into us here at Vacuwash and we check it out for you.

Dodgers, biminis and boat covers have all been subject to a lot of extreme weather conditions over winter, combine this with pollution/mould and the ever persistent problem from birds means that any boat with clean canvas in spring is very lucky indeed.

Many owners had to find out post the April east coast low, what the replacement cost of canvas is (boat related inflation is multiples higher than the official CPI rate). This should be a real incentive to keep your canvas in good condition thereby extending the replacement cycle. Regular washing and reproofing will go a long way towards doing just this, DIY is fine, no pressure hoses though. Canvas too large or too dirty/mouldy, or if you just don't have the time to do it yourself, should be cleaned via the Vacuwash process, the cost of doing so will be returned by increasing the life of your canvas.

Boat canvas needs regular maintenance just like everything else you your boat, restitching, shock cord replaced, any tears/holes repaired etc, this and cleaning should all be done at the same time.

Unsure if cleaning will work? or tried to clean it yourself and still cant get it clean, call us and usually we can get the canvas looking fantastic again, if we cant then we don't charge you.

You wouldn't believe that the pictures below are of the same canvas, cost to client $300.