Collectors are great especially in the morning when I wake up.
Also, when I am too busy to raid or having a shield, at least there is still income.
I understand that raiding can give more, but most of us we don't and can't farm all day, everyday.
I upgraded my mines/collectors aggressively at the very beginning.
But when I reached about lvl 5 mines/colls and about th5, I realized that upgrading mines/colls any further would kill the game for me. Simple calculation revealed that mines/colls gave me about enough resources to keep my 3 builders (I had at the time) busy without any raiding.
Since then I have upgraded gold mines and elixir collectors at the background as low priority tasks.
Now being a "second half" th9, I have focused again on mines/collectors and plan to max them all before going to th10.
DE drills on contrary I have upgraded as soon as possible and have both of them maxed.
So shortly putting, there is a dead spot in the mid-level of the game when there is no point for collectors unless you gem your builders, but it is good idea not to postpone collectors too far.
If you raid alot an have alot of free time you dont have to rely on your colelctors and drills much
IGN Rita
*TH 11- LEVEL 165* Fully Farmed * Started February 2014
BK 40 * AQ 40* GW 20* GG 1.7B+ EE 1.9B+ HH 11M
Highest Trophy 5k+
If you get a shield, you'll get more resources which will at least reduce your loss a little and if its a cheap shield then you profit.
How many of you guys raid for those 8M upgrades and then when you have enough, click on upgrade and then find you don't have enough to continue raiding? most people just stop at this point but leaving collectors un-collected will help to generate some gold or elixir to continue your journey.
Maxing collectors can help in war, those extra hitpoints will amount up and will slow the attacker down. Most attackers overlook collectors but when they start to run out of time in their war attack, those extra hitpoints could prevent you being 3 starred.
My gold mines are 11x2, 10, and 9x3. I have 6 level 8 elixir pumps. I stopped upgrading collectors at th6 or th7, I don't really remember. The only time I do upgrade them is when I go up a th. I time it so all my builders will finish the same time as my th. DE collectors on the other hand are both level 3. I upped those as soon as possible.