"На протяжении последних десяти лет..." - smth continuous / that we used to do again and again (365 days per year / or from time to time) "...мы помогали" (we tried to help, we struggled, normally successfully, sometimes maybe not)

"За последние десять лет" - 10 years have gone and smth was done / achieved
"мы помогли" (cases of all our clients were successfully closed / problems solved)