Delta hedged long straddles

Using a long straddle on a stock that has hit a low of realized volatility, if I identify an opportunity to go long vega at a certain term expiry, using a delta neutral long straddle, how do you all finance the high negative theta?

Currently I have been selling 8 delta strangles on SPY, but I have found managing this strangle is difficult due to recentering and the high increase of the gamma of the position after recentering