Hi Angimon,
When we took over the previous guy had ours done once a year professionally.We bought a "bissell power wash deluxe" from Godfreys, when they had their "super sale"...(every weekend!!) and even though we've replaced the belts once in 3 years it does a good job.We just use the chemicals from there. We've had a few comments on how nice the carpets are, but then we do a 'rolling stock-take' every 6-8 weeks on a rotation. These carpets are OLD, but it does put some life back into them!
good luck