GOevn, looking forward to seeing your Ah reading at your 34,000 miles having only charged on 120vac. My almost three-year-old pack (replaced by Mitsu with a defective cell under warranty on my used i-MiEV due to suspected previous owner's charging habits) shows 39.4Ah with roughly the same mileage as yours. From a practical standpoint, I can't tell the difference in range between now and when it was brand new.
In the early days of the i-MiEV and large-format or large-capacity Lithium battery deployment, there was a lot of discussion regarding charging rates, especially as they affect battery longevity. Some of us adopted your technique (I was one of those), but it has generally been proven to be unnecessary.
To summarize the conclusions: 120vac (1kW) and 240vac (3kW) charging rate differences are insignificant for the 16kWh i-MiEV pack, especially considering that Mitsubishi had designed the pack to be hit with the 50kW CHAdeMO direct dc charge (and, let's face it, while driving the charge/discharge rates are huge). The difference in battery heating between 120vac and 240vac is considered negligible. CHAdeMO could indeed be bad news (and battery temperatures can indeed be seen to rise rapidly while CHAdeMO charging) and thus the CHAdeMO-equipped i-MiEVs are supplied with forced-air battery cooling and on this forum there are a number of threads for aircon air routing modifications to keep our batteries happy.
More importantly from a battery longevity standpoint, I believe there is consensus that the battery should never be charged to 100% and left there fully charged for a significant amount of time, especially in a high ambient temperature environment. Many of us go a step further and normally keep the SoC somewhere between 30% and 70% (for example, I rarely charge above 12 bars and almost never drop below two bars, and have yet to see turtle).
Charging at 120vac is less efficient than charging at 240vac due to overhead losses over the extended period of time that charging takes place; i.e., it costs more to charge at 120vac than at 240vac for the same amount of kWh added to the battery. Despite recognizing that, some of us use the 120vac slow charge in winter to keep the battery warm for the overnight charge.
EVs: 2 Wht/Blu SE Prem., '13 Tesla MS85, 3 156v CorbinSparrows (2 Li-ion), 24v EcoScoot(LiFePO4)
EV Conv: 156v '86 Ram PU, 144v '65 Saab 96
Hybrids: 48v1kW bike
ICE: '88 Isuzu Trooper. Mothballed: '67 Saab (orig.owner), '76 MBZ L206D RHD RV