30 miles a week....its not a lot really (without meaning to discourage or put you down) .
Most of us will settle to an average and it won' change much for years without some serious work. For about 8 to 10 years I averaged 15 to 16 average on 50 mile rides on a roadbike, it never varied much. Only when I started really pushing, seriously, did it slowly edge up.(mind I was probably 45 to 50 by then)
What distances are each ride ?..is it one 30 miler or a few shorter rides a week
Do you commute by bike ?, I always found that a great opportunity to push things along on shorter rides.
In short, more miles, harder pace, more frequent rides but not too frequent at first (don' overdo it in other words, let yourself recover)...theres no shortcut IME but you sound as though you have the desire, use it while its there.
As said up post, winter doesn' help, it' harder to get muscles going, spring and summer will see you improve anyway.