P.P.
I probably depends on your couch. There are "nice" microfiber sofas with brands such as Lane and Ashley and then there are knock offs that are less durable. I have an Ashley microfiber sofa and have had it for about four years. During that time I have washed the coushon covers in the washing maching and dryed them in the dryer 4 or 5 times and they are fine. I probably wouldn't risk it with a knock off brand, though.
I steam clean areas that get dirty that cannot be thrown into the washer - but the washer does a great job on the covers. I use woolite, warm water and a gentle cycle - and dry them in the dryer on medium heat.
Blessings,
P.