Invest Lump-sum or Fund Mega Back Door Roth

[Ms.Fortuna]

Hello,
I am in the process of re financing my mortgage with a cash-out..the reason is that my home equity made 47% of my total net worth (168k equity and $187k invested in 100% stock, total U..S.market index funds)...and I wanted to have more invested in the market instead while mortgage rates are still low.
No intention to stay in the house and sell it after FI, in 6-10 years..
With the re finance, will have 84k available of which 18k  thinking to set aside for EF..
The question is what to do with the rest 66k?
First wanted to invest it all in VTI, now having second thoughts (and am fearful) with the market reaching new " all time high" every day..

The alternative would be to front load contributions to 401(k) to max it to 55k.. I have been using Mega door Roth and was short about 10-12 k a year to max it..So that would mean spreading out that cash over next 6 years (keeping it in a 1.5% savings acct in meantime) and if there is a big market correction in meanwhile, invest whatever is left at once at that point of time?
Which makes more sense?
The new mortgage rate is 3.75%

[Ms.Fortuna]

Thanks, kasperle,
Just curious about your thoughts around why re fi may be not a good idea...if to assume that market on average returns 7%, wouldn't it be good to pool some of the money tied in a low interest mortgage and put it to work?

[Proud Foot]

.....
The question is what to do with the rest 66k?
First wanted to invest it all in VTI, now having second thoughts (and am fearful) with the market reaching new " all time high" every day..

The alternative would be to front load contributions to 401(k) to max it to 55k.. I have been using Mega door Roth and was short about 10-12 k a year to max it..So that would mean spreading out that cash over next 6 years (keeping it in a 1.5% savings acct in meantime) and if there is a big market correction in meanwhile, invest whatever is left at once at that point of time?

I would probably do a blend of both. Max out enough to essentially do a $0 net paycheck the rest of the year and the first 6 months or so of next year while still getting the maximum match from your company.  Figure your cash needs for this time period and then dump the rest into a taxable investment account. 6 years of holding cash is a long time to be losing to inflation.

[Ms.Fortuna]

Kasperle, it does make sense, thanks!

Proud Foot, I like the idea of a blend.