By now I really did expect that my production skills and buildings would finally reached at least level 17 and max it off next week or the week after, but as you can see below I was soooo wrong. XD
The likely culprit behind this I believe is the 'Uranium Mine'. Most often than not, everytime I try to upgrade one production skill or building I would have enough resources except for the bloody Uranium.
Even though my Uranium Building is also at level 15 (same as my other production buildings), the uranium I get in a full day is only 150!!! Yep only 150! I'll be damned, upgrading Copper Mine from level 15 to 16 requires 340 Uranium which means at least 2 days and a half of waiting!!!! T_T
Anyway, I only do check Nextcolony once in the morning and once in the evening to upgrade skills or buildings that are available but it seems when one reaches level 15+ one would really subject to waiting whether they like it or not. XD That's why I'm upgrading the Depots next to store enough resources so I can only check it once every day. Heh! XD