Leaving sill cock faucet open during warm season?

I do a lot of gardening. At our new home, for some reason the sill cock I need to use for my garden hose was installed in an area just off the side of our back deck, just out of arms reach from the deck. It is only accessible by crawling over large rocks with thick ground cover plants, very tedious to get to just for daily waterings.

I connected a 6' garden hose extension to it so that it can be easily used from our deck. At the end I attached a Gardena Y-valve (https://www.amazon.com/Gardena-36938-Garden-Y-Valve-Connector/dp/B00004SDYN/ref=sr_1_fkmr0_2?ie=UTF8&qid=1495487048&sr=8-2-fkmr0&keywords=gardena+y+splitter)

In this configuration it currently does not leak anywhere. If I just leave the bib open so that there's always pressure in the extension during the warm season, am I asking for trouble? Aside from tampering by a stranger or our young ones, do hoses or inline valves like the one I am using tend to just fail or break out of the blue while you're not looking and begin leaking? If so is there an easy way to extend the bib that is more secure and fool proof?

I'm no expert, but I think at the very least you would want to ensure you have anti-siphon capability built into your sill cock to prevent backflow if your supply pressure should drop. Alternatively, you can buy some screw-on adapters that provide the same function. The only other concern I might have is any other contamination that might occur from the garden hose not being as clean as the supply lines, and with an open valve, it could work its way back. I would think with enough regular use the chlorination wouldn't allow anything to grow though, but again, I'm no expert.

As for things failing/leaking, I can't really comment as I've never left my hoses that way.

Until you mentioned backflow, I would never have thought of it as a concern, thanks for pointing that out.