The narrower the range of voltage that you keep the chemistry the better. Anodes stress and strain during li-ion intercalation, and these maximize at full charge and discharge. Of course keeping the battery within, say 20-30% soc range at all times (e.g only use it from 40-70% charge) isn't practical. I do wish that phone and laptop firmware allowed a setting to stop charging at a point less than 100%...
The other consideration is that the soc meters drift, so every so often it is essential to do a full cycle in order to calibrate it. The batteries should be good for 500-1000 full cycles, so it shouldn't be an issue. The smaller the partial cycle, you get to 10k or 100k of them before the battery is condemnable.