We recommend waiting until after the scheduled Wednesday maintenance to ensure this change has gone through before purchasing your Runes.
2 Days of casual gameplay, sure. If you like/do log in everyday and do your dailies.
45 dailies is at least 4 hours. LFR is at least 4 hours, raiding if you have a team is probably another 6 to 9 hours. that's for 1 toon. Every further toon that you want to alt gear another 8 hours per week.
1 toon, 18 hours.
2 toons, 26 hours.
Starting to feel a bit like a job. On my alt I have to optimize for the non thunder dailies because my healer doesn't burn through the mobs like my dps toon does. I basically stop doing dailies on my alt because I couldn't pull the 90 runes. This might entice me to do it every other week.