There are a couple reasons your dryer could be taking longer to dry.
1) Your dryer vent hose is clogged with lint and needs to be cleaned in order to maximize airflow and that will make your dryer more efficient.
2) If your dryer vent hose is not clogged up then it is possible that your dryer mat need to be retired and replaced with a new one. Don't jump to this conclusion right away, have your dryer vent checked first.
The reason your dryer smells like smoke is because the lint is getting trapped behind the tumbler where the heating element is. The reason the lint is getting trapped is because your dryer vent hose is clogged with lint or possibly a bird's nest and has nowhere to escape. The lint gets trapped on the tumbler and the heating element dries it out and the lint begins to catch fire.
Warning!!! Stop using your dryer the moment you smell any smoke coming from inside your dryer! Lint is very flammable and will ignite!
The reason your dryer hose is collecting water is because the hose has a sag creating a "U" shaped valley and the condensation from the dryer will collect over time storing more and more water. If water is allowed to sit in your pipe the following problems may occur:
1) Water sitting in a metal pipe will cause rusting and will eventually eat holes in the pipe. If water collects in a vinyl hose, holes will also result from dry rotting.
2) Once a pool of water forms the lint gets mixed in creating a form of sludge making any air getting through almost impossible. Drying time will be dramatically affected and create the illusion your dryer needs to be cleaned. Running a brush through the hose with a brush will not solve the problem.
Solutions for this problem are:
1) A temporary solution (if the sag can't be corrected) is to crawl under the house and poke a little drain hole at the lowest part of the "U" where the water is collecting. The water will drain out allowing the air to move more freely. The condensation will keep collecting and draining out of the hole and may possibly make a tiny hole bigger.
2) The best solution is to fix the sag in the pipe. Fixing the sag may be as easy as raising the hose making it level with the rest of the hose. If there are obstructions in the way of leveling out the hose then rerouting the hose altogether may be the only alternative.
***The cost of rerouting a hose depends on the length of the run and how far one has to crawl under the house. This procedure may be an initial cost but will save lots of money in the long run.
Warning!!! Water that lingers and becomes stagnant in the hose can create lots of bacteria like staph and tetanus. Exercise extreme precautions when going near the laundry vent if you smell stagnant water. Call a professional to correct the problem