So I skipped my weekly water changes for a month, I went a total of 4 weeks with no negative side effects. The only thing it may have changed is my gH it is on the rise since I add a LOT of top off water to this open top aquarium. It went from 90ppm to 140ppm, I did a 20% water change and I still have to test the water to see if the gH dropped any. This seems to be the only thing I need to keep in check, along with TDS which should be taken care of by monitoring gH I hope...I do not actually have a TDS meter yet.
I have only one complaint over the last month and I am not even sure the lack of water changes is the factor. I am getting yellowing elder leaves and pinholes, my Java Fern is actually killing off some of its leaves entirely. This to me is a nitrate/potassium deficiency however some plants act up if your water gets too hard so I am not sure right now.
I carried out this experiment on TWO 5 gallon tanks I have, and I can say without a doubt it did not effect my nitrate readings on either tank. One stayed at almost 0ppm and the other never crept above 5ppm. I tested every week throughout the month and it never rose higher than 5ppm.
Conclusion is I will be dialing back my water changes to once a month, I literally vac my substrate maybe twice a year. Tanks are clean as a whistle too!