how long should cycling take? Stalling and low heat issues

Jofish Member Posts: 1
I have a new 60L tank and started cycling it 6 wks ago. I am doing a fishless cycle and the ammonia has cycled through and is now back to 0 ppm after peaking at 4ppm approx .The nitrites have risen as expected to or above 5ppm (my testing kit goes no higher so Im not sure of the exact amount). The nitrites have been high for about 2-3 weeks and still no sign of reducing. The nitrates have finally risen over the past 10 days to 40 ppm. So I have expected the nitrites to drop but there is no signs of this happening and its been 6 wks since i started the cycling process. Ive seeded the tank at the start, plus added quick start and added an old filter from my other tank in another effort .. to try and speed up the process. It is very cold at our place at the moment...mid winter Melbourne... gets down to single figures over nite... so am wondering if that is slowing it all down too much . Should I get a heater to help speed up the process. Ive also heard that the process can stall midcycle if there is too much ammonia /nitrites... is this true and if so, how will I know if thats what is happening here. Any advice would be greatly appreciated.
Regards, Jo