Android phone between 5k - 7k with good battery backup

[kkn13]

i too have a lumia 720 since more than 1.5 yrs. its low RAM makes it bad for multi-tasking and install 30+ apps it slows down like hell.

its better now with wp8.1, would have dumped it had it stayed any longer on older versions.

have you tried hard reset and restore? mine is fine here
i also have a L820 and the speed difference isnt much,dunno why yours is slow,i guess its due to cluttered cache files(happens over time)
though i do remember it was slow as hell on WP8,WP8.1 is amazing but once i did a restore,it was even better