@David Piqueira Your strategy/approach is the same as mine! Slow and steady wins the race. Plus, if a 15% return really is feasible for performing notes, that's double the long-term historical average stock market return--not too shabby!
It's easy to get drawn in by the potential of big returns from NPNs, but it's important to keep your goals in mind too and, similarly, what kind of returns you need to be earning to reach your goals. If your goals require you to "only" need to be earning a 12% return, then taking on additional risk of NPNs for a 20% return might not be worth it to you. A lot of the financial podcasts I listen to (particularly Stacking Benjamins) emphasize this mindset. They claim that people too often just save or invest without any idea of how much they'll really need to reach their goals. The argument is that if you work backward from your goals, instead of just saving/investing without a plan, then you can (hopefully) come up with an intelligent plan and increase your chances of actually reaching your goals.
Good luck to you!