If you’re ever in doubt about whether to repair or replace, consult a professional. They can give you the best advice based on your situation!
Is there a particular time of year that’s best for window maintenance? I imagine extreme weather could be an issue.
Great question! Spring and fall are ideal for maintenance when the weather is milder. Avoid winter to prevent damage from freezing temperatures.
I like to use a mix of humor and maintenance work to keep the mood light while inspecting! Makes hauling a ladder a bit more bearable! 
Haha, that’s the spirit! It’s all about making the task enjoyable, right?