I'm working with Orcad Capture and Pspice 16.3 and I have two different issues I want to discuss with you:

1) the first one concerns problems I'm frequently experiencing with Pspice's simulation results. I'm working with the following circuit:

that is a triangle waveform generator in which I've put a memristor replacing one of the resistor of the Schmitt Trigger. The circuit is quite simple, maybe except for the differential equation (defined in memristor model implementation) the tool is required to solve in order to guarantee the correct simulation of the memristor behaviour in the circuit. Once I am able to simulate the circuit avoiding the convergence problems the differential equation involve, I've noticed that many of the simulation results depend on the time simulation I've chosen: for example the period of the output waveform is 97ms when I simulate the circuit for 5 seconds and it magically become 105ms when I increase that time up to 8 seconds and 116ms with 12 seconds of simulation. I know that the tool work with some approximation algorithms but I think that the difference I got among the different results is not negligible! How is that possible? Any possible explications?

2) the second issue also concern simulation results: in another circuit what I expect to find as output is a waveform with time-varible period and time-variable peak, that is a waveform with period and peak that increases or decreases proceeding in the time simulation of the circuit. Since among mesurement results I can only select and display a single value for each variable of the simulated waveform there is a way in Pspice or exporting the results in other tools/software to analitically verify the change of period/peak with time simulation?

Thank you for your attention.