The only downside is the extra wear and tear on your hard drive. If you have 8GB of RAM, that means 8GB of data will be written to disk every time you go into hibernation and will be read again when starting up. Over a year, that would mean a couple of extra Terabyte of IO on your disk.
On a 100GB SSD with a 100000 write cycles using the above 8GB scenario, that'll reduce your write cycles by about 30/100000 per year, about 0.03% lifespan reduction per year, which is not too bad.