Many of you gave me some great advice about bottles and how to keep them straight between the two boys.
In the end, I've opted to just "muddle through" until Isaac is weaned. He is already drinking out of a cup now and then so I am hoping this will happen soon. I already own all the ADVENT bottles I need and just didn't want to buy more in order to have different styles for both boys. It does create a lot of trickiness, but saving the money was worth it to me.
Isaac still gets a little upset if a bottle comes out for Elijah and not for him. I try to time it so Isaac gets to drink some when I feed Elijah. Or he has already eaten and just has no interest in more milk when Elijah's bottle comes out. Sometimes he just has to get upset for awhile if none of these options are possible. Cheerios helps greatly in the distraction process.
As we await complete weaning, I have six bottles for Isaac and six bottles for Elijah. I had smaller bottles for Elijah but then he decided he wanted six ounces to drink instead of four. Thus the bigger bottles like big brother's had to come out. The smaller ones only hold up to four ounces.
The nipples look exactly the same. But they aren't. Isaac's is a size 4. Elijah's is a size 1. The nipple size is very important as it determines how fast the liquid comes out.
Unfortunately, the ADVENT people didn't think seeing the number on the nipple was incredibly important. They designed it so the only way you can read the size is to hold the nipple up under bright light, spin in circles three times, and make a wish.
Okay, not exactly, but I think you get my point.
I tried to wash them in "groups" to prevent this intense nipple studying every time I washed bottles. But it just doesn't work that way. By mid morning, I usually have 5-7 bottles to wash. That's enough to get a load done and into the sanitizer (a Godsend might I add!) So I have decided to just wash, sanitize, and then study the nipples before putting Isaac's up on the left side of the counter and Elijah's on the right.
If they go into the fridge because they weren't finished, Isaac's go on the second shelf and Elijah's on the first. JB started to tell me that this was backwards, but I told him that it was already imprinted into my brain, and he was going to have to adjust. I think he could tell by looking at my face how serious I was about my new system and so he fell into line without questioning any further.
But I did want to thank everyone for the input! It's so great to know that I have a village behind me as I raise my boys.