Usually if any index makes a new high, such a record should be printed at favorable market internals. For example the number of share issues printing new records should be larger than the number printed at the previous pick.
Let me look at Nasdaq 100:
As the table shows, today Nasdaq 100 had less new highs (185 issues) then previously (228 new highs on Aug 2, 2013). It does not look healthy when Nasdaq 100 is 46% higher than nearly two years ago but the number of new highs is 19% lower then previously. Additionally, the number of new lows is really puzzling. The index makes new record but as far as 63 issues print their lows.
The same situation occurred at S&P 500. Although this index did not make a record today (not yet) but the last record, made on May 21, 2015, had 30 issues making their lows. Today as far as 132 issues printed their lows. Well, this index is very close to its record but the number of companies going down is increasing.
I do not know how high this market will go but it is definitely not a healthy market. What is more, these internals have been worsening for many, many months.