I have had this dryer for at least 10 years and it just now started to give me problems. I put it on for 180 minutes, regular dry and it heats but not enough to get the clothes dry... I have to add another 20 to 30 minutes to get them totally dry... Is it time for a new dryer or can I save this one??

First thing to do is to examine whether the vent pipe is still attached to the exit pipe in the wall. Sometimes the vent piping is possibly made of plastic material that deteriorates, has holes or otherwise is damaged to the point it no longer accepts the venting steam.
If it has just come away from the connection at the wall, the simple solution is to just re-connect.
Sometimes these connections come away because the piping has lost its tie to the wall pipe. The wall pipe, usually of aluminum, as it heats, might be causing the vent piping to lose contact.
The plastic piping is usually of accordion type; i.e. it expands to accommodate the space between the machine and the wall pipe. Sometimes, because of its closeness, the accordion plastic piping gets jarred loose when the machine is shoved back into its position. The attachment to each pipe must be carefully affixed.

Sometimes, because of lint and other material that might clog the exit pipe, inside as well as close to the outside vent, it clogs up with such matter.
It might be an idea to shove a vacuum tube ---if you have such attachment-- through each end of the system to see if you can draw any material that might clog up the piping in its length of exiting.
Otherwise, remove the outside vent cover and take a look to see if there is any material in the pipe there. Otherwise shove a vacuum tube up there, see if any material is clogging. Such clog would without question, cause decreased amount of steam to exit and cause increased time of drying.

Does it vent through the roof? Most vents have a screen to prevent birds/pests from entering. Check to see if the screen is clogged with lint. I have to clean mine every 3 months.

Thanks to both of you... Everything is attached to where it belongs and it vents out under the house, it doesn't seem to be clogged as air passes through easily... What about the thermostat, could that been the problem??

It could be one of the thermostats. Check those with an ohm meter. If they are OK they will show continuity, if not, replace