DIY Soldering

I've only done a little bit of soldering, but this is the first time it is something that will eventually be covered up.
We are remodeling our master bath and as such I'm putting in two new faucets (Bath and Shower). Everything is soldered up. I only needed to 'manually' solder two joints. The rest were the neat little fittings that have solder in them already.
I slowly turned the water on and ran the faucets turning them on and off several times. No leaks so far.
It'll be about a week before the walls are covered up. Am I correct in assuming that if a leak is to spring up it'll happen within the next week?

TIA!

Jason

generally speaking if it doesn't leak within 30 min you are OK.

Those pre-soldered fittings are a gimmick that the box stores are featuring. I say gimmick because they really don't save any work and cost more. All you have to do to get a good sweat joint is clean the fitting and pipe well, use plenty of flux, heat the joint until the heated joint will cause the solder to flow around the joint. Remove the heat and let the joint set before moving it. You can use a wet rag to clean the excess flux and smooth the solder as long as you don't move the joint until it is cool. I might use more solder than a pro, my joints may not always look like a pro did the work, but they don't leak.

joints

Your assumption is correct 99% of the time, but I have seen many joints that looked good, and did not leak at first, but after months or years did start leaking, or even separate. In one case it took about 22 years, even though the joint was so poor that at that time it just took a small bump against the copper to break the connection.

I've always used a light even application of flux on both fittings, is it better to use "plenty", as advised above?

The flux deoxidizes the fitting as it heats which allows the solder to a) flow easily and b) bond. In my experience, it's easy to underflux and hard to overflux. I put good smears of flux in the fitting and on the outside of the pipe. If you get a little squeeze out when you slide the pieces together, it's enough.