Having similar problem. I am in perth and have cement tile roof, had it recoated about 10 years ago.  now paint faded, moss growing on tiles so decided I would maybe replace with colorbond.  Now I am more confused than ever with what I should do.  Roof restoration guy today said they would do all the maintenance and a painter using their paint would paint separate as they don't recoat over another companies paint!!!!! Before to day I had quotes for colorbond of $25,000 up to $28,000 and that is not with engineer fee, indemnity insurance and site plans having to be submitted.  So it has gone up to about $30,000.  To have roof recoated via this companies painter and having them maintain it first,, it looks like $5000 .  My question is which is better in the long term.  Getting each companies speels and I really am more confused than ever.  Lets face it paying $5000 is better than $30000 but not if it doesn't last at least 10-15 years like my last one.  Colorbond only guaranteed about 20 years I think.