in my first year I worked about 80% of my weekends. now I do not try to do so but sure I read almost every single day. however working in biology sometimes you have to go to the lab in weekend to check on your growing material, change buffer, change temperature etc..
to be honest, I feel excited and motivated the more I get positive results and sometimes I do not want to stop working!! out from work I swim, watch movies, shopping,visiting freinds.