I don't have a specific issue but looking ahead to a doc I will be cutting and wondering what's the best workflow if i have a mixture of 1080 and 4k sources on a 1080 timeline (or even a 4k timeline) - if I'm having some lagging in playback of the 4k sources, would a good practice to be create proxies for those 4k clips and switch over to proxy mode when needed (realizing entire timeline wouldn't be proxy)? or maybe render and replace (even if no effects on it)? Does one method make more sense than the other?
Probably not in need of taking a proxy edit off site or anything so creating proxies for 5 years worth of footage doesn't seem like the best idea, but I am thinking maybe on specific clips I end up using in the edit it might be helpful... I know I can also reduce the playback quality but just exploring options. I haven't don't extensive editing in Premiere, but well versed in Avid and FCP7.
I'd go with proxies... they exist for exactly what you describe. Render and Replace is more for interchange with After Effects, when having AE Comps in the timeline slows things to a crawl. I know you can use it for other workflows, but its really not tested extensively for anything other than its intended purpose.