Timeline roadmaps result in a constant barrage of deadlines resulting in:

Made up release dates
Development death marches
Mismanaged expectations
Missed market opportunities
Building the wrong things
Sad product managers

And it leads to a vicious cycle that can be hard to get out of:

No one wants to be caught holding the hot potato, missing a deadline, so bigger and bigger buffers are given.

Developer thinks it'll take 5 days, tells you 7, you put 10 on the roadmap just to be safe

Time expands to fill the work given.

This is called Parkinson’s Law, and is the reason you always seem to be running up against deadlines, no matter how far out they started.

It's a combination of scope creep and procrastination dynamics, and is unfailingly true

Longer estimations create longer, riskier looking timelines.

Your execs are now even less comfortable giving freedom to build in lean ways, so try to tie down even tighter deadlines so they feel they have control on their resources and costs

There’s never room for discovery in here, no time for rework or quality, and so the wrong things are built, problems aren’t solved, and quality suffers.

You might be shipping a lot, but you're shipping shit

This leads to Blame Culture, where no one feels safe being the one to make a misstep at work, having been told off for missing the last deadline and launching features that aren't solving anything...

This is the opposite of psychological safety

GOTO .... people resort to giving bigger buffers and estimates for their work, in hopes they don’t get it wrong ever again

This vicious cycle loops 'round and 'round until everyone quits and you're left with a pile of junk for a codebase.

Deadlines = Technical Bankruptcy

Okay, I left this on a pretty sombre note, so I'll follow up with some ways to actually break out of this cycle and get back to a healthier way of working:

Here's a thread I did earlier on ditching timeline roadmaps and moving to a lean format: https://twitter.com/simplybastow/status/1168531714832027648

And here's how to reframe the thinking around deadlines = incentive to work (hint: they aren't!) https://twitter.com/simplybastow/status/1321105770570809344