Yeah I was exactly the same, and was considering a Predator for ages but then just went custom when I realised I'd end up with something far more reliable, not to mention look better. Never was a fan of those black tubes, and the QDC versions are just ugly IMO.
Thanks. I've actually sold my Titanium build now, but you'd get a good 12 months or so, perhaps longer, before having to change coolant like the one I used (Mayhems Clear Blue UV). The Ice Dragon Nano I have in my 6700k loop at the moment they say is good for 2 years, not that I'll be going that long as I will add a GPU to the loop sometime... either 1080Ti or VEGA probably.
Coolants such as Aurora have a much shorter lifespan though, some say only a few months or so. They are more for show builds though, not really intended for long term home use.