Battery lifespan

I've been reading through the posts regarding battery lifespan, but have the following question I've not been able to find an answer to...

I tend to use my phone a lot during the day at work where I'm able to keep the phone on charge. I understand even when on charge the drain is from the battery and not the charging circuit. Also that a partial charge with the new li-on batteries doesn't have a negative impact on lifespan, so charging often and keeping the phone topped up seems to be the best option. (caveat that you do a full battery charge once a month to refresh the state)

The question I have is regarding the top 20% where the battery is trickle charged. It seems to me that the battery drain is slower during usage in this region also. Is that true and if so, does keeping the phone charged reduce the overall amount of charge/discharge cycles and hence proving a longer life?