OP i have same worries as you. I am young and not only did i max out Roth IRA, I have contributions to VINIX and just put money in fidelity spartan funds in taxable account and I feel I should market time as well. While long-term you shouldn't worry, it'd be a gamble to wait it out and miss out gains as well. Though I know next to nothing about economics and observe the noise to get some idea of influences on the market, to me it doesn't seem we are on path to sustainability and i believe there's a big bubble coming up.
Yeah im sorta one of those believers in a bubble, i wasn't around to call bubbles in 2011-12 (i think people mistook poor economy as recovering from recession) but a bubble is coming sooner than later i think. a growing number of people i know in my age group have difficulty finding work in a field once touted as a great career, now there's calls for a bubble and high unemployment in my career which is already happening. healthcare field as a whole is bubbling with soaring student debt and many professionals like nurses unable to find work though baby boomers and ACA blunted unemployment a little, it doesn't keep pace with supply of healthcare students entering field. Some research articles in academic journals are already sounding alarms. In the end, it'd probably be like law school where some schools are closing and students are bargaining tuition down because they have leverage. healthcare jobs are no longer what it used to be though much better than other fields too. wages are flat too not helping to solve problem. market maybe going up because 1% have more free money to invest and speculate than ever. gas prices down, stimulate economy?! Illegal immigrants will drain us! North Korea will start war! Russia started war (what happened since then?), QE is gone, market is fake propped up by the Fed, Wall St (those insiders) are giving less bonuses to employees, etc etc.
Lot of noise, some of it very concerning and very true, some not worth it, and concerning is long-term growth especially w/some students with 200k debt and no asset to collect unlike housing. auto loans are now creeping up to. despite globalization, lack of jobs, un/underemployment, huge backlog of students competing for jobs with students who can't find any, flat wages, increasing gap, for all the facts that are true and bad and will bite us, my thinking is that this money i'm not touching anyway and i wasn't going to do anything w/it anyway. if market goes down, i'll just plow my cash and bonds back to stock anyways and ride the next wave up. i'm in this for long haul, why do i care about a bubble coming up? Only care about bubble if losing your job so focus on that. your job will bring in more $$ and peace to mind than ROI so focus on career. if you're too old though then yeah you're pretty screwed. I read a 38 yr old healthcare manager lost 150k/yr job, single family income, kids, no savings, will last a year before bankruptcy, can't find job b/c too old and so many young students, so it's really important to SAVE because soon with so many students, 40 will be the new 55!