I bought an 8 week springer into the mix nearly 7 weeks ago - I have a 3 year old Sprocker who I also had as a pup.
If I knew then what I know now, I wouldn't have done it - but then I look at her and she is just so cute and lovely. But she doesn't sleep well at night, and I'm knackered!
She gets on well with the other dog, who has been really good with her, but I'd truly forgotten how hard puppies were. Things like, planning to go out, feeding times are different as pup on 4 meals a day, having to plan double walking as older dog needs more exercise than the pup, the teething (she's a proper land shark!), and definitely the sleeping!
Sleeping - If I'm lucky if she goes 10-4, then wees and poos, then back to sleep until about 6. If I'm not lucky, 2am, 4am, 6am. I know she's only 15 weeks, but it has been way harder than I remembered, and also it's just me and young adult kids who are rarely here.
I do wfh so that helps.
She is absolutely lovely, but it has been very hard. I know (hope) it will only get better as she gets older. Luckily for a springer she can be quite chilled too, as the sprocker is a total chiller, but equally they are absolutely manic between 7pm and 8pm at night when I want to sit down and relax! That hour nearly kills me....