I used to play Minecraft with very good FPS with normal render distance and fast graphics without optifine. over time i have had to decrease the render distance and download optifine because it starts lagging. I am now playing on Short render distance with no lag but anything else and i will get lag. Why is minecraft lagging the more i play? This happened over time btw not quickly!
Have you updated java and the 64 bit java (if you needed that)
Is your computer getting older since "over time" your performance has degraded..
Have you updated video card drivers
It's not just a simple game
There is billions or trillions of blocks each of which you can't see that your computer renders and continuously keeps loading
update java and clear cache and update graphic drivers
and check if its still laggyhttp://www.piriform.com/ccleaner
http://addpcs.com/software/tfc/
Some pretty
Good
Cleaners there
Also have you defragmented your computer lately?
it's recommended to defrag every monthIs anything else lagging on the computer
Browsers
Any other games? To indictact it isn't just minecraft
But possibly a virus or defrag needed or cache needs cleaning
Or general obvious thing all computers performance degrades over timeAlso update texture packs/mods
And yes, over time as a general rule, your computer just slows down
i have 64 bit java not sure if it is updated but i will check that and i will try defragmenting my computer thanks for the help!!