Do you keep your trendlines?

Was wondering if you guys keep your trendlines on your charts. Meaning, between august 11 to 23, a certain pair observed a upsloping channel before breaking the support at say 1.4010

So when that happens, you draw a horizontal line to mark that level

Just thinking if a trendline from days, weeks or months ago would be valid in the present.

Thoughts?

Yea, i keep them, i have one chart only for that purpose, it's interesting how price reacts with old trendlines, upper/lower channel lines etc., but i don't take trades just based on trendlines, they are just for confluence.

No, I don't keep them. TL's may last on average from 100 to 1000 bars.
Old ones may be hit, but not fully understood, so I tend to drop them after major reasons are done with.
I'm on the 1'TF, so this may not apply to you.

The whole idea of supports and resistances is that they are based on historical prices, whether it is a weekly, daily or intra-day chart. Of course, nothing guarantees that history will repeat itself but many investors put their automatic orders on levels that are clear resistance or support. Therefore, these levels tend to actually act as support or resistance so you should definitely consider them when you analyze a chart.

it seems to me that the master trader in regards to trendlines is user wmd.

I have daily S/R lines drawn months ago that still get respected today. It may just be a hesitation before moving on, but the market sees it and seems to respond. If nothing else, they make great targets when considering take profit.