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tokens: it is difficult to assess the probability that such candidates will be confirmed as pulsars, because confirmation strategies differ between surveys and usually limit the number of reobservations n REOBS to a handful because of constraints on telescope time. As a result, in an extreme case like PSR J1929+1357, the probability of confirming a discovery is approximately , so that the probability of making a confirmed discovery is . In 2013, with and a reasonable value of , the probability of making a confirmed discovery of a pulsar was 3 × 10 −4 . We note that, ideally, reobservations should also be made on a specifically designed set of timescales in order to capture pulsars with the wide range of switching timescales that we now see to be possible in this class of objects. In the case of PSR J1929+1357, it was fortunate that the pulsar was ON during the second attempted reobservation; in the next 93 observations, it was OFF. Had the first 5 reobservations been unsuccessful, it is possible that even such a strong pulsar would remain unconfirmed. Similar pulsars, but with one tenth of the flux density, must surely exist and would be clearly detected in the survey observations, particularly with the high sensitivity of the Arecibo Telescope used for the PALFA survey, but the case for extended reobservation efforts would be even less compelling: unconfirmed detection would be attributed to radio-frequency interference or to the detection of a normal pulsar in a distant sidelobe. For these reasons, there may be as many as several thousand strong pulsars like PSR J1929+1357 in the sky, which happen to be OFF when surveyed or, if ON, are OFF during confirmation observations. Similar but less severe selection effects preventing the discovery of objects like other long-term intermittent pulsars also contribute to what must be a population of neutron stars of significant size compared to that of normal pulsars. As we noted earlier, RRATs also suffer similar selection effects in one-pass surveys. It is likely that UTMOST (Caleb et al. 2016 ) and upcoming new projects, like CHIME (Bandura et al. 2014 ) and MeerTRAP (B. W. Stappers et al. 2016, in preparation) on MeerKAT, will be useful for finding more such objects as they will make many searches of the same piece of sky on various timescales for single-pulse and periodic sources. The discovery of two new long-term intermittent pulsars, PSRs J1910+0517 and J1929+1357, significantly expands the known population of such objects, whose properties are summarized in Table 2 . Although their number is still small (only five such pulsars), we are now in a position to make a few general remarks regarding their properties. They seem to have a rather narrow range of spin periods, from about 0.3 to 0.9 s. Furthermore, there seems to be a positive correlation between the spin period and its derivative, as we can see from their ON positions in the P – diagram (Figure 7 ). This correlation is similar to that observed